Trends in the Periodic Table

Question 1

Atomic Radius

Answer 1

Atomic radius of an atom is the distance from the nucleus to just beyond the outermost electrons (valence electrons)

Question 2

Atomic Radius in Diatomic molecule

Answer 2

Atomic radius of an atom is the distance from the nucleus to just beyond the outermost electrons (valence electrons)
In a diatomic molecule (such as N2, or oxygen, O2), the atomic radius is the distance between the two nuclei, divided by 2

Question 3

Atomic Radius Left-to-right in a period:

Answer 3

More protons in the nucleus for the same number of energy levels = the ENC increases, stronger attraction between nucleus and electrons = smaller atomic radius

Question 4

Atomic Radius Top-to-bottom in a group:

Answer 4

The number of energy levels increases = weaker attractive force due to increasing number of shielding electrons = larger atomic radius

Question 5

Ionic Radius

Answer 5

Size of atom after ion formation depends on whether a cation (+) or anion (-) was formed

Question 6

Ionic Radius: Cations

Answer 6

Cations are always smaller than their original neutral atoms
Cation has one less energy level than the neutral atom
The same ENC is now shared among less electrons, so force is slightly higher on each one; nucleus pulls the electrons more closely

Question 7

Ionic Radius: Anions

Answer 7

Anions are always bigger than their original neutral atoms
The same ENC is now shared among more electrons, so force is slightly weaker on each one; nucleus cannot hold electrons quite so close

Question 8

Cation Formation

Answer 8

.

Question 9

Anion formation

Answer 9

.

Question 10

Ionization Energy

Answer 10

Ionization energy is the amount of energy required to remove an electron from an atom or ion in the gaseous state
The amount of energy depends on which electron is being removed

Question 11

Ionization Left to Right

Answer 11

Ionization energies increase left-to-right across a period
ENC increases, so valence electrons are more strongly attracted to the nucleus, and thus more energy is required to remove an electron from the atom. The energy required to remove an electron increases when ENC Increases.

Question 12

Ionization top to bottom

Answer 12

Ionization energies decrease top-to-bottom in a group
Atomic radius increases, so the attraction between the valence electrons and nucleus becomes weaker, and thus less energy is required to remove the first valence electron. Nucleic force is weaker and it is easier to remove electrons.

Question 13

Electron Affinity

Answer 13

Electron affinity is the energy change that occurs when an electron is accepted by an atom in the gaseous state
When an electron is added to a neutral atom in the gaseous state, energy is usually released

Question 14

Electron Affinity top-to-bottom

Answer 14

Electron affinity decreases top-to-bottom in a group
Atomic radius increases, so there is a weaker attractive force between the nucleus of atom and the new electron, and thus the atom is less willing to spend energy to add an electron

Question 15

Electron Affinity left-to-right

Answer 15

Electron affinity increases left-to-right across a period
ENC increases, so the force of attraction between the nucleus and the valence electrons increases, and thus the atom is more willing to spend energy to add an electron

*Noble gases are an exception

Question 16

Electronegativity

Answer 16

In 1922, an American chemist, Linus Pauling, proposed a way of quantitatively describing the ability of an atom to attract electrons when bonded, combining ionization energies, electron affinity, and some other measures of reactivity
This scale is referred to as electronegativity

Question 17

Electronegativity and Fluorine

Answer 17

Pauling assigned a value of 4.0 to fluorine, the element considered to have the greatest ability to attract electrons within a chemical bond

Electronegativity values for all other elements were assigned relative to the value for fluorine
In other words, electronegativity is NOT a measurement (ie. unitless)
just a number to describe who has a greater pull in a bond.

Question 18

Electronegativity top-to-bottom

Answer 18

Generally Decreases

Question 19

Electronegativity left-to-right

Answer 19

Generally Increases

Question 20

Why does Electronegativity increase/decrease in a group/period?

Answer 20

Same reasons as for trends in ionization energy and electron affinity! (atomic radius and ENC, respectively)

Question 21

Metallic Reactivity Top-to-Bottom

Answer 21

Reactivity increases top-to-bottom in a group
ENC stays the same, more electrons are added to farther shells = less hold on electrons, allows metals to readily give up electrons

Question 22

Metallic Reactivity Left-to-Right

Answer 22

Reactivity decreases left-to-right in a period
ENC increases, electrons are added to same shell and held tightly = more difficult for metals to give away electron

Question 23

Non-Metallic Reactivity Top-to-Bottom

Answer 23

Reactivity decreases top-to-bottom in a group
ENC stays the same, more electrons are added to farther shells = less hold on electrons harder for non-metals to gain an electron

Question 24

Non-Metallic Reactivity Left-to-Right

Answer 24

Reactivity increases left-to-right in a period
ENC increases, electrons are added to same shell and since electronegativity increases across a period, non-metals will react to gain electrons

Question 25

Overall Reactivity (Most reactive metals, non-metals?)

Answer 25

The most reactive metals are the largest since they are the best electron givers.
The most reactive nonmetals are the smallest ones, the best electron takers.