Periodicity

Question 1

What is periodicity?

Answer 1

The repeating pattern of chemical and physical properties of elements across a period in the periodic table.

Question 2

What are the trends in atomic radius across a period?

Answer 2

Atomic radius generally decreases across a period due to increasing nuclear charge and constant electron shell number.

Question 3

What is the trend in electronegativity across a period?

Answer 3

Electronegativity generally increases across a period.

Question 4

What is the trend in melting points of period 3 elements?

Answer 4

Melting points increase from sodium to silicon, then decrease for phosphorus, sulfur, and chlorine.

Question 5

What is the trend in reactivity of Group 2 elements?

Answer 5

Reactivity increases down the group due to increasing atomic radius and decreasing ionization energy.

Question 6

What is the trend in reactivity of halogens?

Answer 6

Reactivity decreases down the group due to increasing atomic size and decreasing electronegativity.

Question 7

How do halogens react with halide ions?

Answer 7

Displacement reactions, with a more reactive halogen displacing a less reactive halogen.

Question 8

What is the electronic configuration of chromium?

Answer 8

[Ar] 3d5 4s1 (exception to the rule).