Chapter 3.2 - Periodicity - Periodic Trends

Question 1

What is Atomic radius?

Answer 1

Distance from center to the outer most region

Question 2

What is the trend of atomic radius down a group?

Answer 2

Atomic radius increase down group from top to bottom. Each new period begins with new energy level which is farther from nucleus, increasing atomic radius.

Question 3

What is the trend of atomic radius across a period?

Answer 3

Atomic radius decreases across period from left to right. Nucleus’s positive charge is greater relative to charge of electrons in same shell, pulling electrons closer to nucleus and thus reducing atomic radius

Question 4

What is Ionic radius?

Answer 4

Distance from center to the outer most region in ion

Question 5

What is the trend of ionic radius for cations?

Answer 5

Radii of cations (e.g. Mg+) are smaller than their parent. This is because there are more protons than electrons in the cation, so valence are more strongly attracted to nucleus.

Question 6

What is the trend of ionic radius for anions?

Answer 6

Radii of anions(e.g. Cl–) are larger than their parent. This is because the extra electron in the anion results in greater repulsion between valence electrons, thus larger radius.

Question 7

What is first ionization energy?

Answer 7

The amount of energy required to remove one mole of electrons from one mole of gaseous atoms to form one mole of 1+ ions
electron on right side.

Question 8

What is second ionization energy?

Answer 8

The amount of energy required to remove one mole of electrons from one mole of 1+ ions to form one mole of 2+ ions.

Question 9

What is the trend of ionization energy down a group?

Answer 9

IE decreases down a group from top to bottom. This is because atomic radii increase down group, making easier to remove electron. Also because of shielding effect weakens forces between nucleus and outer electrons.

Question 10

What is the trend of ionization energy across a period?

Answer 10

IE increases across period from left to right. This is because since electrons are pulled closer to nucleus (see atomic radius), more difficult to remove them.

Question 11

What is electron affinity?

Answer 11

The change in energy released which accompanies addition of an electron to an atom in gaseous state. electron on left side.

Question 12

What is the trend in electron affinity down a group?

Answer 12

Decreases down a group from top to bottom (becomes less negative. With some exceptions)

Question 13

What is the trend in electron affinity across a period?

Answer 13

Increases across a period from left to right (becomes more negative. With some exceptions)

Question 14

Trend in reactivity down group 1

Answer 14

Reactivity increases down a group due to atomic radius making it easier to lose an electron.

Question 15

Trend in reactivity down group 7

Answer 15

Reactivity decreases down the group due to atomic radius which makes it difficult to gain an electron.

Question 16

What is electronegativity?

Answer 16

Relative attractions that an atom has for a shared pair of electrons in a covalent bond.

Question 17

Trends of electronegativity down a group

Answer 17

Electronegativity decreases down a group from top to bottom. This is because atomic radii increase down group, making easier to remove electron. Also because of shielding effect weakens forces between nucleus and outer electrons.

Question 18

Trends of electronegativity across a period

Answer 18

Electronegativity increases across period from left to right. This is because since electrons are pulled closer to nucleus (see atomic radius), more difficult to remove them.

Question 19

Metal + Oxides ->

Answer 19

Base

Question 20

Non-metal + Oxides ->

Answer 20

Acid

Question 21

Trend in metallic character across period

Answer 21

Decreases

Question 22

Trend in metallic character down a group

Answer 22

Increases

Question 23

Non-metal oxides + water ->

Answer 23

Acidic solutions

Question 24

Metal oxides + water ->

Answer 24

Basic solutions

Question 25

How does melting point change down group 1

Answer 25

Melting point decreases

Question 26

How does melting point change down group 7

Answer 26

Melting point increases

Question 27

First ionization energy equation for Non metals

Answer 27

X(g) –> X+(g) + e-

Question 28

First ionization energy equation for Metals

Answer 28

X(g) + e- –> X+(g)