1.7 Periodic Trends in Atomic Properties

Question 1

atomic radius

Answer 1

The distance from the centre of an atom to the outermost electrons

Question 2

how to find atomic radius

Answer 2

The distance between two nuclei of the same atom bonded together (in a metallic or covalent bond) is divided by two and this value is the atomic radius

Question 3

Atomic radius __________ down a group

(valence electrons are ____________ by electrons in lower orbitals, causing them to be _______ from the nucleus)

Answer 3

increases; shielded/repelled; further

Question 4

Atomic radius __________ from left to right across a period

(additional protons ________ the force of attraction between electrons and the nucleus.

Although electrons are also added to the valence shell, since they are added in the same shell, there is no net change in the “shielding effect” and the additional electron repulsion are negligible
compared to the increase in + charge)

Answer 4

decreases; increase

Question 5

effective nuclear charge

Answer 5

The net force experienced by an electron in an atom due to the positively charged nucleus

Question 6

how to calculate effective nuclear charge

Answer 6

formula:

nuclear charge(atomic #) - inner shells = ENC

e.g. phosphorus

15 - 2 - 8 = +5
(don’t count valence electrons)

Question 7

Ionic radius

Answer 7

The distance from the centre of an ion
to the outermost electrons

Question 8

why are cations SMALLER than their original atoms?

Answer 8

force of attraction between the nucleus and the electrons is shared with less electrons, so the force on each electron increases, pulling them closer to the nucleus

Question 9

why are anions LARGER than their original atoms?

Answer 9

the force of attraction on each individual electron
decreases, causing them to go further from the
nucleus

Question 10

ionization energy

Answer 10

The quantity of energy required to remove an electron from an atom or ion in the gaseous state

Question 11

what is 1st ionization energy?

Answer 11

it’s the energy required to remove the most
loosely held electron, 2nd ionization energy corresponds to the second most loosely held electron, and so on.

Question 12

Why does ionization energy DECREASE down a group?

Answer 12

it takes less energy to remove an electron because of the “shielding effect” (decreasing force of attraction between nucleus and electrons)

Question 13

why does ionization energy INCREASE from left to right across a period?

Answer 13

force of attraction between electrons and nucleus increases from left to right across a period

Question 14

electron affinity

Answer 14

energy change that occurs when an electron is added to a neutral atom in the gaseous state

Question 15

1st , 2nd, electron affinities refers to…

Answer 15

the energy change when a first or second
electron is added to the neutral atom

Question 16

If the attractive force between the added electron and the nucleus is greater than the repulsive force between the added electron and other electrons in
the atom, energy is _________

Answer 16

released

Question 17

why does electron affinity INCREASE from left to right across a period?

Answer 17

Force of attraction between the nucleus and an added electron increases, while repulsive force between electrons is the same

Question 18

why does electron affinity DECREASE down a group?

Answer 18

Force of attraction between nucleus and an added electron decreases, while repulsive forces between
valence electrons and lower orbits increases called “shielding effect”