Why is it not to use resolidified sample in melting point determination

Answers

Answer 1

Answer:

It is advisable to use a fresh sample and not a re-solidified one when determining melting point of a substance because when the sample is melted once, it changes its crystal lattice structure to a certain extent. This can cause it to melt at a different temperature the second time around, which will not be an accurate reading.

Explanation:

The temperature at which a substance changes state from its solid form to its liquid form is known as the melting point for that substance. At this temperature, a pure substance will have both its solid as well as liquid states existing in equilibrium with each other.

When a pure, crystalline sample is melted the first time to determine its melting point, its crystal lattice structure gets distorted to a certain extent with the rising temperature. Even if cooled and re-solidified, this original crystalline structure will not melt at the same temperature it did earlier. This is because its crystal lattice is different this time around, leading to an incorrect melting point reading.


Related Questions

in an experiment an unknown organic compound was found to contain 0.12g of C, and 0.02g of hydrogen . calculate the empirical formula of the compound.if the rfm of the compound was found to be 56, find the molecular formula of the compound

Answers

Answer: C4H8

Explanation:Please see attachment for explanation

Final answer:

To find the empirical formula, the moles of C and H are calculated and their ratio determines that the empirical formula is CH₂. The molecular formula is found by dividing the compound's relative formula mass (56 g/mol) by the empirical formula mass (14.026 g/mol), which suggests the molecular formula is C₄H₈.

Explanation:

To calculate the empirical formula of the unknown organic compound, we begin by determining the moles of carbon (C) and hydrogen (H) in the sample. Using the atomic weights of carbon (12.01 g/mol) and hydrogen (1.008 g/mol), we find:

Mo: 0.12g C (1 mol C / 12.01 g C) = 0.01 mol CMo: 0.02g H (1 mol H / 1.008 g H) = 0.02 mol H

The ratio of moles of hydrogen to carbon is 0.02 mol H / 0.01 mol C = 2:1. Therefore, the empirical formula is CH₂.

To find the molecular formula, we divide the relative formula mass (rfm) of the compound by the empirical formula mass. The empirical formula mass of CH₂ is 12.01 (for 1 C) + 2 * 1.008 (for 2 H) = 14.03 g/mol. Dividing the rfm (56 g/mol) by the empirical formula mass (14.03 g/mol) gives approximately 4. Therefore, the molecular formula is C₄H₈, as we multiply the subscripts in the empirical formula CH₂ by 4.

Forensic science is the application of science to what field?
OA. Biology
OB. Criminal Justice
C.
Art History
OD. Philosophy

Answers

Answer:

it's criminal justice

Explanation:

Forensic science, also known as criminalistics, is the application of science to criminal and civil laws.

Final answer:

Forensic science is the application of science to B. Criminal Justice.

Explanation:

Forensic science is a multidisciplinary field that applies scientific principles and techniques to solve crimes and aid the criminal justice system. It encompasses various specialties, including DNA analysis, fingerprint examination, ballistics, and toxicology, helping investigators gather evidence, identify suspects, and ensure justice is served in criminal cases.

It involves the use of scientific methods and techniques to examine and analyze evidence in criminal investigations. Forensic scientists apply their knowledge in disciplines such as biology, chemistry, physics, and even mathematics to help solve crimes and provide evidence in legal proceedings.

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Mercury has one of the lowest specific heat capacities. If 257 J of heat are added to 0.45 KJ of mercury, the Mercury’s temperature will increase by 4.09 K. What is the specific heat capacity of mercury?

Answers

Answer:

139.67 (J/kgk)

Explanation:

Given data:

mass of mercury = m = 0.45 Kg

Amount of energy = Q = 257 J

Increase in the temperature = ΔT = 4.09 K

To find:

Specific heat capacity = C

Formula:

By using specific heat equation,

Q =  m x C  X  ΔT

C =  Q  /  m  x  ΔT

   = 257J  /  o.45 kg  x  4.09K

   = 257J  / 1.84

    = 139.67 (J/kgk)

Specific heat of mercury is 139.67 (J/kgk).

Many plants are poisonous because their stems and leaves contain oxalic acid, H2C2O4, or sodium oxalate, Na2C2O4; when ingested, these substances cause swelling of the respiratory tract and suffocation. A standard analysis for determining the amount of oxalate ion, C2O42-, in a sample is to precipitate this species as calcium oxalate, which is insoluble in water. Write the net ionic equation for the reaction between sodium oxalate and calcium chloride, CaCl2, in aqueous solution. (Use the lowest possible coefficients. Omit states-of-matter in your answer.)

Answers

Answer:

H₂C₂O₄ + Ca²⁺ ⟶ CaC₂O₄ + 2H⁺

Explanation:

There are three steps you must follow to get the answer.

You must write the:

Molecular equation Ionic equation Net ionic equation

1. Molecular equation

H₂C₂O₄(aq) + CaCl₂(aq) ⟶ CaC₂O₄(s) + 2HCl(aq)

2. Ionic equation

You write the molecular formulas for the weak electrolytes and solids, and you write the soluble ionic substances as ions.

H₂C₂O₄(aq) + Ca²⁺(aq) + 2Cl⁻(aq) ⟶ CaC₂O₄(s) + 2H⁺(aq) + 2Cl⁻(aq)

3. Net ionic equation

To get the net ionic equation, you cancel the ions that appear on each side of the ionic equation.

H₂C₂O₄(aq) + Ca²⁺(aq) + 2Cl⁻(aq) ⟶ CaC₂O₄(s) + 2H⁺(aq) + 2Cl⁻(aq)

The net ionic equation is

H₂C₂O₄ + Ca²⁺ ⟶ CaC₂O₄ + 2H⁺

The net ionic equation is;  Ca^2+ (aq) + C2O4^2-(aq) -------> CaC2O4(s)

First we must put down the molecular equation as follows;

Na2C2O4(aq) + CaCl2(aq) ------> 2NaCl(aq) + CaC2O4(s)

The total ionic equation is;

2Na^+(aq) + Cl^- (aq) +  Ca^2+ (aq) + C2O4^2-(aq) -------> 2Na^+(aq) +  Cl^- (aq) +  CaC2O4(s)

The net ionic equation is;

Ca^2+ (aq) + C2O4^2-(aq) -------> CaC2O4(s)

The spectator ions in this reaction are Na^+ and Cl^-, they appear on both sides of the reaction equation and they do not appear in the final net ionic equation.

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When nitrous oxide is converted to nitrogen and oxygen, what is the term used to describe the oxygen atoms formed?


A) Reactants

B) Products

C) Intermediates

D) Activated complexes

Answers

Answer:

B) Products

Explanation:

Nitrous oxide is colorless gas.

It is also called laughing gas.

It is used in medicine specially in pain relief.

It is also used by dentists.

Chemical equation:

2N₂O   →   2N₂ + O₂

Here nitrous oxide is converted into nitrogen and oxygen. Nitrous oxide is reactant and nitrogen and oxygen are product.

The given reaction is decomposition reaction of nitrous oxide.

Decomposition reaction:

It is the reaction in which one reactant is break down into two or more product.

AB → A + B

Answer:

intermediates

Explanation:

Hey gradpoint :)

[A]a[B]b [C]c [D]d

When the Keq value is large, the number representing [A]a[B]b must be (larger or smaller) than the number representing [C]c[D]d. This relationship means that the (reactants or products) must be favored and that the mixture at equilibrium is largely (reactants or products).

Answers

Answer:

Smaller; products; products  

Explanation:

aA  + bB ⇌ cC + dD

[tex]K_{\text{eq}} = \dfrac{\text{[C]}^{c}\text{[D]}^{d}}{\text{[A]}^{a}\text{[B ]}^{b}}\\\\\text{When the $K_{\text{eq}}$ is large, the number representing [A]$^{a}$[B ]$^{b}$ must be $\textbf{smaller}$ than the}\\\text{number representing [C]$^{c}$[D]$^{d}$. This relationship means that the $\textbf{products}$ must be favoured}\\\text{and that the mixture at equilibrium is largely $\textbf{products}$.}[/tex]

In the mathematical equation showing that volume (V) divided by temperature (T) remains equal to a constant (k), volume and temperature are _______________ proportional

Answers

Answer:

Directly  

Explanation:

[tex]\dfrac{V}{T} = k[/tex]

If V increases, then T must also increase to keep the same ratio.

If V decreases, then T must also decrease to keep the same ratio.

V and T are directly proportional, because a change in one always causes a change in the other and the changes are in the same ratio. The constant k is called the proportionality constant.

Help please I need the answer

Answers

Answer:

                    Polyatomic Ionic Compound

Explanation:

                     In given statement the compound given is called as Sodium oleate this means that when Oleic acid is treated with NaOH then it forms.

                     In chemistry there are few species which are involved in the formation of compounds.

  (i) Atoms:

                  It is very common that atoms of different elements combine to form compound through covalent bond. For example, H₂, O₂, N₂, F₂ e.t.c.

   (i) Ions:

                  Other than covalent compounds we have ionic compounds. Ionic compounds are made up of ions. These ions forming the ionic compounds can be monatomic like Na⁺, Br⁻, Mg²⁺, Al³⁺, N⁻³ or they can be polyatomic like CO₃²⁻, SO₄²⁻, NH₄⁺, PO₄³⁻ e.t.c.

    (iii) Polyatomic Ions:

                                     In polyatomic ions we find a charge on a molecule which contains two or more atoms bonded covalently. Hence, in given compound we have a long chain of molecule containing a negative charge neutralized by opposite +ve charged sodium ion. Hence, Sodium oleate is a polyatomic ionic compound.

Sort the sentences based on whether they are correct or incorrect.

Answers

Answer:

Explanation:

Correct statements:

Water boils at a temperature below 100°C at higher altitude.

Water boils at a temperature 100°C under normal pressure.

The density of water decreases on freezing.

Water expend on freezing.

False statements:

Water contract on freezing.

calculate the molecular mass of Na2HPO4

Answers

Answer:

Molar mass of Na2HPO4=141.96, of Na2HPO4. 12H2O = 358.14: so to get the same 0.4 M: 28.65/358.14*141.96 g, add water until you reach 200ml , dissolve all solid and then filter to make sterile.

Explanation:

141g/mol is the molecular mass of Na[tex]_2[/tex]HPO[tex]_4[/tex].  It is also known as molecular weight. It is computed by multiplying the mass of every atom.

What is molecular mass?

The quantity of mass associated with such a molecule is referred to as its molecular mass. It is also known as molecular weight. It is computed by multiplying the mass of every atom by the amount of atoms from the element in the molecule. Water, for example, is composed of two hydrogen atoms and one oxygen atom.

The total of the atomic weight of the atoms within a molecule yields the molecule's molecular mass. The molecular mass expresses the mass of such a molecule in relation to the mass of both the 12C atom, which itself is assumed to be 12.

Molecular mass = Molar mass of sodium×2+ molar mass of hydrogen + molar mass of phosphorus+ 4 molar mass of oxygen

Molecular mass = 23×2+1 + 30+ 4× 16=141g/mol

Therefore, 141g/mol is the molecular mass of Na[tex]_2[/tex]HPO[tex]_4[/tex].

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the elements fluorine,chlorine,bromine,and iodine are all found in the same group on the table. these elements are grouped together because they​

Answers

Answer:

Fluorine, chlorine, bromine and iodine are grouped together because they have the same number of valence electrons.

Explanation:

Fluorine, chlorine, bromine and iodine are all found in group 7, which is the second-last column from the right. Group 7 elements are also called the "Halogens" family.

The group number also tells you the number of valence electrons that the elements have in that group. Valence electrons mean the outermost electrons (See picture).

For example, fluorine has two shells (the circles with dots on them). The outermost electrons, or valence electrons, are the dots on the biggest circle. There are 7 dots, so there are 7 valence electrons, which corresponds with Group "7".

A full shell (except the for first shell) is when there are 8 dots. Since 7 is so close to 8, Halogens are very reactive.

Fluorine, chlorine, bromine and iodine all have 7 valence electrons and are in the Halogens family, which are very reactive.

Final answer:

The elements fluorine, chlorine, bromine, and iodine are grouped together because they belong to the same group on the periodic table and share similar chemical properties.

Explanation:

The elements fluorine, chlorine, bromine, and iodine are grouped together because they belong to the same group on the periodic table.

These elements are part of Group 17, also known as the halogens. They share similar chemical properties due to having the same number of valence electrons.

For example, they all have seven valence electrons, which allows them to easily gain one electron to achieve a stable electron configuration like the noble gas neon.

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Please Solve #3 please

Answers

3. Cl will form ionic compound by gaining one electron from the cation.

Explanation:

The chloride ion can be formed by gaining an electron during ionic bond formation.

Chlorine has 7 electrons in its outermost shell thereby requiring only 1 electron to complete its octet.

Electronic configuration of chlorine is 1S2,2S2,2P6.3S2,3P5

Chloride is an anion formed when chlorine element gains an electron or when compound like NaCl dissolves in water Sodium ions (cation) and chloride ions(anion) is formed.

In ionic compounds only electrons take part ie they move from one atom to another.

The _____ identifies an element.

Answers

Answer:

protons

Explanation:

Four moles of iron metal react with three moles of oxygen gas to produce two moles of iron (III) oxide. What is the balanced equation for the formation of rust?

Answers

Answer:4 Fe + 3 O2 => 2 Fe2O3

Explanation: The number of atoms are now balanced.

The balanced chemical equation for rust formation is 4 Fe(s) + 3 O2(g) → 2 Fe2O3(s).

The balanced equation for the formation of rust, which is iron (III) oxide, from iron metal and oxygen gas is represented as:

4 Fe(s) + 3 O2(g) → 2 Fe2O3(s)

This shows that four moles of iron (Fe) react with three moles of oxygen (O2) gas to produce two moles of iron (III) oxide (Fe2O3), which is the principal component of rust. Rusting is a redox reaction where iron is oxidized, and oxygen is reduced. The process is accelerated by the presence of water and electrolytes, leading to the hydrated form of rust represented by Fe2O3 · xH2O(s), where x varies indicating the hydration level.

Rust does not form a protective layer over the iron, which means that unlike the patina on copper, iron continues to corrode as the rust flakes off and exposes the fresh iron underneath to the atmosphere.

What happens to iron when it melts?

Answers

When iron melts in 912 degrees Celsius, in starting the atoms of the iron become more packed and then in 1,394 degrees Celsius, the atoms loose again and melts.

What is melting?

Melting is a process by which the substance that is in solid starts to become liquid. The changing of the solid into liquid is called melting. Usually in high temperature, the substance starts to melting.

Thus, when iron melts in 912 degrees Celsius, in starting the atoms of the iron become more packed and then in 1,394 degrees Celsius, the atoms loose again and melts.

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Which equation is derived from the combined gas law?
OV, T = P₂72
O Pq V, T, - P ₂ V2 T 2

Answers

Answer:

[tex]\frac{p_1 V_1}{T_1}=\frac{p_2 V_2}{T_2}[/tex]

Explanation:

The equation of state (combined gas law) for an ideal gas states that

[tex]pV=nRT[/tex]

where

p is the gas pressure

V is the volume of the gas

n is the number of moles of the gas

R is the gas constant

T is the absolute temperature of the gas

The equation can be rewritten as

[tex]\frac{pV}{T}=nR[/tex]

For an ideal gas that undergoes a transformation, if the amount of gas remains the same, the term on the right of the equation remains constant. This means that the ratio

[tex]\frac{pV}{T}[/tex]

for the gas remains constant, and therefore we can rewrite the equation as

[tex]\frac{p_1 V_1}{T_1}=\frac{p_2 V_2}{T_2}[/tex]

where 1 indicates the initial conditions of the gas while 2 indicates the conditions of the gas after the transformation.

Answer:

f

ExplaOV, T = P₂72

natifon:

Ok, so anyone who knows anything about radiation science knows it is deadly because it is rapidly replacing its neutron, while it does this it releases protons and electrons ( I think, correct me if I'm wrong ), so my question is, how is this deadly to humans, how is exposion to protons and electrons deadly?

Answers

Radiation science is deadly to humans/ living organisms because it can cause damage to our cells and cancer.

Explanation:

The ionization of materials, basically replacing neutrons while it releases protons and electrons can cause the emission of harmful radiations, basically neutron radiation, proton radiation, X-rays, high-speed electrons gamma rays. These waves are extremely harmful to humans. Being exposed to these waves for a long time can cause cancer and also tissue damage. The above-mentioned waves are extremely powerful since it is capable of breaking chemical bonds. It can change the composition and chemical structure of animal cells. This would lead to harmful health problems.

Write a mathematical equation showing that pressure (P) multiplied by volume (V) remains equal to a constant (k).

Answers

Answer:

did you get the answer?

Explanation:

?

The mathematical expression of Boyle's law is a constant pressure and constant volume, which can be showed as: P V = k, where P is pressure, V is volume and k is a constant.

What is Boyle's law ?

According to Boyle's law, the volume of a given mass of a dry gas at constant temperature is inversely proportional to its pressure. At moderate pressures and temperatures, most gases behave like ideal gases.

The technology of the 17th century was incapable of producing extremely high pressures or extremely low temperatures.

This empirical relationship, established in 1662 by physicist Robert Boyle, states that the pressure (p) of a given quantity of gas varies inversely with its volume (v) at constant temperature; in equation form, pv = k, a constant.

Thus, This means that for a constant pressure, a constant volume must be kept.

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What is the definition of an “atom”?

Answers

An atom is the smallest unit of matter that has the properties of an element

Answer: The indivisible unit of matter.

Explanation:

89.6 of H2O determine the number of moles

Answers

Answer:

true ?

can you give me brainiest

The chart show the masses and velocities of two colliding
objects that stick together after a collision
According to the law of conservation of momentum, the
momentum of the object after the collision is
kg. m/s.
Mass (kg) Velocity (m/s)
L 200
15
150 |

Answers

The momentum of the object is 1500 kgm/s.

Explanation:

The law of conservation of momentum states that without effect of any external force in the system, the momentum of the system remains conserved. And momentum is defined as the product of the mass and velocity of the object.

Here, the mass of the 1st body = 200kg.

The mass of the 2nd body = 150kg.

Velocity of the 1st body = 15 m/s.

Velocity of the 2nd body = - 10 m/s.

So, the total momentum of the system before collision = [tex]200\times15 + 150\times{-10[/tex] kgm/s

= 1500 kgm/s.

After the collision, the body sticks together.

So, the total mass =200+150 kg = 350 kg.

Momentum remains conserved. So the momentum of the body= 1500 kgm/s.

Choose all the answers that apply.

Earth's water:

is reused and recycled
is mostly freshwater
is strongly attracted to other materials
has a neutral pH value
can dissolve more substances than any other liquid

Answers

Answer:

- is reused and recycled

- can dissolve more substances than any other liquid

Explanation:

Earth water is reused and recycles in the form of the water cycle (hydrological cycle). In this cycle, water from the earth surface evaporates in the atmosphere, cool and condense into cloud or snow and fall to the earth surface.

As a universal solvent, water can dissolve more substances than any other liquid. The polar arrangement of oxygen and hydrogen atom in the water molecules makes it excellent salt.

On Earth, ~2.5% is a freshwater whereas 97.5% is salt water. The pH of water differs for surface and salt water, i.e. neutral to alkaline respectively. Water molecules attract to other water molecules better than the other substances. Therefore, other options are incorrect.

Answer:

recycled and reused

strongly attracted to itself  

not attracted to other materials

easily dissolved in other liquids

Explanation:

13._SeClo+ _02 → _SeO2 + _Cl2

Answers

Answer:2,2,2,1

Explanation:

Answer:

4SeClO + 2O2 → 4SeO2 + 2Cl2

What is the molality of a solution made by dissolving 137.9g of sucrose in 414.1g of water?

Answers

Answer: 2.71 moles of solute for every 1 kg of solvent.

Explanation: As you know, the molality of a solution tells you the number of moles of solute present for every 1 kg of the solvent.This means that the first thing that you need to do here is to figure out how many grams of water are present in your sample. To do that, use the density of water.500.mL⋅1.00 g1mL=500. g Next, use the molar mass of the solute to determine how many moles are present in the sample.115g⋅1 mole NanO385.0g=1.353 moles NaNO3So, you know that this solution will contain 1.353moles of sodium nitrate, the solute, for 500. g of water, the solvent.In order to find the molality of the solution, you must figure out how many moles of solute would be present for 1 kg=103g of water.103g water⋅1.353 moles NaNO3500.g water=2.706 moles NaNO3You can thus say that the molality of the solution is equal to molality=2.706 mol kg−1≈2.71 mol kg−1 The answer is rounded to three sig figs.

Maurice rolls a bowling ball with a mass of 9 kg down the bowling lane. The ball strikes all 10 pins and Maurice gets a strike. The balls acceleration was 12 m/s^2. With what force did Maurice throw the bowling ball?

Answers

Answer:

108 N

Explanation:

F = m × a

Force equals mass × acceleration, for more you can see Newton's second law.

what charge will a group 16 anion have​

Answers

Answer: Group 16 elements form ions with a 2 - charge.

Explanation: Therefore each of these elements would gain one electron and become an anion with 1 - charge.

what happed on monday march 10 2010​

Answers

Answer: Carlos Slim becomes the first Mexican and person from an emerging economy to top Forbes Richest Person list, with net worth of US$53.5 billion

Answer: Carlos Slim becomes the first Mexican and person from an emerging economy to top Forbes Richest Person list, with net worth of US$53.5 billion

Determine the molar mass of a compound that has a density of 0.1633 g/L at STP.
(show work)

Answers

Answer:

                     M.Mass  =  3.66 g/mol

Data Given:

                  M.Mass  =  M = ??

                  Density  =  d  =  0.1633 g/L

                  Temperature  =  T  =  273.15 K (Standard)

                  Pressure  =  P  =  1 atm (standard)

Solution:

              Let us suppose that the gas is an ideal gas. Therefore, we will apply Ideal Gas equation i.e.

                                             P V = n R T    ---- (1)

Also, we know that;

                       Moles  =  n  =  mass / M.Mass

Or,                                   n  =  m / M

Substituting n in Eq. 1.

                                             P V = m/M R T   --- (2)

Rearranging Eq.2 i.e.

                                             P M = m/V R T   --- (3)

As,

                     Mass / Volume = m/V = Density = d

So, Eq. 3 can be written as,

                                             P M = d R T

Solving for M.Mass i.e.

                                             M = d R T / P

Putting values,

M  =  0.1633 g/L × 0.08205 L.atm.K⁻¹.mol⁻¹ × 273.15 K / 1 atm

M  =  3.66 g/mol

Explain in detail what information can be learn about atoms of different elements by examining the periodic table. For the maximum points earned, you should include the visible information on the periodic table as well as trends of the atoms(size, energy levels, valence electrons, etc,)
WILL MARK BRAINLIEST IF I GET AN A!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!‍‍‍

Answers

Answer:

See below this long answer.

Explanation:

These are the main features of the periodic table that you will be able to relate with some property trends of the atoms like size, energy levels, valence electrons, electronegativity, and ionization energy.

A) Features:

1. Elements are arranged in increasing order of atomic number, i.e. number or protons.

2. Since atoms are neutrals, the number of electrons equals the number of protons, and, as result, the elements are arranged in increasing order of number of electrons.

3. The elements are arranged in 18 columns and 7 rows.

4. The rows are named period and correspond to the principal energy level (n): first row corresponds to n = 1, second row corresponds to n = 2, third to n = 3, and so on up to n = 7. The number of elements in each period are:

Period 1, n = 1, 2 elements

Period 2, n = 2, 8 elements

Period 3, n = 3, 8 elements

Period 4, n = 4, 18 elements

Period 5, n = 5, 18 elements

Period 6, n = 6, 32 elements (this includes the 14 lanthanides)

Period 6, n = 7, 32 elements (this includes the 14 lanthanides)

That makes a total of 118 elements.

5. The columns are named groups and they indicate the number of valence electrons

Group 1: 1 valence electron

Group 2: 2 valence electrons

Group 13: 3 valence electrons

Group 14: 4 valence electrons

Group 15: 5 valence electrons

Group 16: 6 valence electrons

Group 17: 7 valence electrons

Group 18: 8 valence electrons

Groups 3 through 12 includ the transition metals and due they have subshells that are not completely filled, their valence electrons vary.

More like a reference than as a rule these are the number of valence electrons for these groups.

Group 3: 3 valence electrons

Group 4: 2-4 valence electrons

Group 5: 2-5 valence electrons

Group 6: 2-6 valence electrons

Group 7: 2-7 valence electrons

Group 8: 2-3 valence electrons

Group 9: 2-3 valence electrons

Group 10: 2-3 valence electrons

Group 11: 1-2 valence electrons

Group 12: 2 valence electrons

B) Property trends

1. Atomic radius (size)

Down a period (from left to right): due to the increase of the positive charge (number of protons) while the main energy level (n) does not change, the electrons in the valence shell feel a stronger atraction to the nucleus causing that the atomic radius decrease from left to right.

Down a group (top to bottom): due to the increase of the main energy level, the outermost orbital is bigger and the atoms become bigger. Thus the trend is that the atomic radius increase when you go down a group.

2. First ionization energy

Down a period (from left to right): due to the increase of the nuclear charge (such as explained above) the greater attractive force makes that, in general, the first ionization energy increase from left to right.

Down a group (top to bottom): due to the increase in the size of the atom, , generally, the energy to remove an electron from the outermost shell, decrease.

3. Electronegativity

This is the relative ability to atract electrons in a covalent bond. It increases from left to right and from bottom to top: the most electronegative atoms is fluor.

Which statement best describes a chemical reaction?
In a chemical reaction, one or more substances called products are combined or
broken down to form reactants.
In a chemical reaction, one or more substances called products are combined or
broken down to form compounds.
In a chemical reaction, one or more substances called reactants are combined or
broken down to form products.
In a chemical reaction, one or more substances called reactants are combined or
broken down to form elements.

Answers

Answer:

In a chemical reaction, one or more substances called reactants are combined or  broken down to form products.

Explanation:

Chemical reaction:

In a chemical reaction one or more substance converted into the another substance.

The substances that reacts or combine during the chemical reaction are called reactants while the new species formed as a result of chemical reaction are products.

There are different types of reaction given below:

Decomposition reaction:

It is the reaction in which one reactant is break down into two or more product.

AB → A + B

Synthesis reaction:

It is the reaction in which two or more simple substance react to give one or more complex product.

Single replacement:

It is the reaction in which one elements replace the other element in compound.

AB + C → AC + B

Double replacement:

It is the reaction in which two compound exchange their ions and form new compounds.

AB + CD → AC +BD

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