8.3 Trends in Three Atomic Properties

Question 1

atomic size

Answer 1

how closely one atom lies next to another

Question 2

How to find atomic size

Answer 2

measure the distance between atomic nuclei in a sample of an element and divide that distance in half

Question 3

metallic radius

Answer 3

used for metals; one half the shortest distance between nuclei of adjacent, individual atoms in a crystal of the element

Question 4

covalent radius

Answer 4

used for elements occurring as molecules (nonmetals); one-half the shortest distance between nuclei of bonded atoms

Question 5

How atomic size changes varies for MAIN-GROUP elements (changes in n)

Answer 5

as the principal quantum number (n) increases, the probability that outer electrons spend most of their time farther from the nucleus increases as well; thus atomic size increases

Question 6

How atomic size changes varies for MAIN-GROUP elements (changes in Zeff)

Answer 6

as the effective nuclear charge (Zeff) increases, outer electrons are pulled closer to the nucleus; thus, atomic size decreases

Question 7

Why is it that down a group, n dominates?

Answer 7

move down a main group, each member has one more level of inner elctrons that shield the outer electrons very effectively
*atomic radius generally INCREASES down a group

Question 8

Why is it that across a period, Zeff dominates?

Answer 8

across a period from L to R, electrons are added to the same outer level, so shielding does not change
*atomic radius generally DECREASES across a period