3.3: Periodic Trends

Question 1

What is ionization energy?

Answer 1

the energy required to remove an electron from an atom in the gaseous state

Question 2

What is atomic radius? What two factors affect it?

Answer 2

the distance from the nucleus to the outside of the atom

two factors affect atomic radius:
1) as n increases, the atomic radius increases
2) Zeff (effective nuclear charge) - the net force of attraction between electrons and the nucleus; affected by # of protons and inner electron shielding

Question 3

When does ionization energy increase and decrease?

Answer 3

• decreases DOWN a group (increases up a group) corresponding with increased radius and decreased Zeff
• increases from LEFT TO RIGHT across a period corresponding with decreased radius and increased Zeff

Question 4

When does atomic radius increase and decrease?

Answer 4

• increases DOWN a group
• decreases from left to right across a period (increases from right to left) as shielding is constant, however, Zeff increases due to more protons

Question 5

What is electron affinity?

Answer 5

change in energy that accompanies the addition of an electron to an atom in the gaseous state

Question 6

When does electron affinity increase and decrease?

Answer 6

• increases as you go UP a group and from left to right of a period
  (not a very consistent trend)

Question 7

What is metallic character/reactivity of metals? When does it increase and decrease?

Answer 7

metals tend to readily lose electrons during chemical reactions compared with non-metals due to the low ionization energies of metal

~ increases DOWN a group and from RIGHT TO LEFT across a period

Question 8

What is electronegativity? When does it increase and decrease?

Answer 8

an indicator of the ability of an atom to attract shared electrons

~ increased UP a group and from LEFT TO RIGHT across a period