Isotopes and Trends

Question 1

What is an Isotope?

Answer 1

atoms of the same element - same # of protons, different # of neutrons

Question 2

How do you find abundance? state what x represents

Answer 2

formula:
Abundance = mass of iso¹ (x) + mass of iso² (1 - x)

*x represents the abundance of the first isotope, and since it’s a % (1 - x) is essentially 100 - x in order to find isotope 2 (so do that)

Question 3

What is the unit for isotopes

Answer 3

u - unit or amu - atomic mass unit

Question 4

How do you find avg atomic mass

Answer 4

(Mass of iso¹ × abundance¹/100) + (Mass iso² × abundance²/100) = avg atomic mass

Question 5

What are the 5 sorts of trends of the periodic table?

Answer 5

Atomic radius, ionization energy, electron affinity, electronegativity, and the shielding effect

Question 6

What is atomic radius?

Answer 6

It is the distance from nucleus to nucleus with 2 atoms’ valence shell touching each other.

Question 7

What is atomic radius measured in?

Answer 7

Picometers (pm)

Question 8

What happens to atomic radius when moving left to right and why

Answer 8

It decreases. Electrons and protons are added 1 by 1 to the same shell and can’t shield each other from being attracted to their opposite. This makes nuclear charge (protons basically) go up which decreases atomic radius

Question 9

What happens to atomic radius when moving up to down and why

Answer 9

It increases. Increasing electrons means increasing shells and electrons further away from the nucleus. Just think radius; by design it sort of makes sense. bigger circle = bigger radius

Question 10

What is ionization energy?

Answer 10

The energy required to remove the 1st valence electron from a neutral atom. The closer the electron is to the nucleus the more energy is required for it to be removed

Question 11

What is ionization energy measured in

Answer 11

KJ/mole (kilojoule)

Question 12

What happens to ionization energy when moving left to right and why

Answer 12

Increase. This is because atomic radius decreases, which means the valence is closer to the nucleus and more strongly drawn in

Question 13

What happens to ionization energy when moving up-and-down and why

Answer 13

Decrease. Because the atomic radius increases, so valence becomes further away so the nucleus has less of a pull

Question 14

Why does group I have low ionization energy?

Answer 14

Because when an electron is lost it forms a stable octet, so the hold on the valence isn’t so strong. They all want to be stable all the time.

Question 15

What is electron affinity?

Answer 15

It is the ability of an atom to accept an electron, and the energy absorbed or released in the process.

Question 16

Which family has the lowest electron affinity and why

Answer 16

Alkaline earth metals. You’d think it’s Group I, but they’re quick to lose an electron and become positive, which attracts electrons. Group II isn’t as quick to do that, so they attract the least electrons

Question 17

What is electronegativity?

Answer 17

It is the measure of attraction of an atom to the electrons in a chemical bond. Closely related to ionization energy.

Question 18

What happens to electronegativity when moving from up to down

Answer 18

It decreases. Atomic radius increases making electrons further from the nucleus and the nuclear charge decreases as well

Question 19

What happens to electronegativity when moving left to right and why

Answer 19

It increases. Atomic radius decreases and nuclear charge increases, attracting more electrons to itself

Question 20

What is effective nuclear charge and what should you know about it

Answer 20

The attractive positive charge of nuclear protons acting on valence electrons
- The effective nuclear charges is always less than total # of protons present in nucleus due to the shielding effect
- Effective nuclear charge is behind all other periodic table tendencies

Question 21

What is the shielding effect charge and what should you know about it

Answer 21

The lessening of attraction between nuclear protons and valence electrons by partially or fully filled inner shells

• Shielding effect increases with the number of inner shells of electrons
• Same shell electrons do not shield each other

Question 22

What is isotopic abundance?

Answer 22

the amount of a given isotope of an element that exists in nature, expressed as a percentage of the total amount of this element

Question 23

how to find average atomic mass? (isotopes)

Answer 23

A = (mass of iso¹)(% of iso¹)+(mass of iso²)(% of iso²)
*repeat equation with mass x % if theres more isotopes

Question 24

what happens to x in an equation of one isotope if there is 3 isotopes you need the abundance of? (2 are the same abundance)

Answer 24

1 - 2x

because it is x, but 2 are the same so it will be -x, and -x, which is 2x minus 100, so, 1 - 2x