Topic 3/13: Periodicity

Question 1

Define atomic radius.

Answer 1

The distance from the nucleus to the outermost electron

Question 2

Define ionic radius

Answer 2

The distance from the nucleus to the outermost electrons in an ion

Question 3

Define electron affinity

Answer 3

The energy released when one mole of an electron is added to one mole of gaseous atom

Question 4

Define electronegativity

Answer 4

The power of an atom to attract a shared pair of electrons in a covalent bond

Question 5

Describe the arrangement of the periodic table.

Answer 5

• list of chemical elements
• arranged in order of increasing atomic number
• sorted into groups and periods

Question 6

Describe the trend of atomic radius.

Answer 6

down a group

• number of electron shells increases ➜ atomic radius increases

across a period

• electrons added to same main energy level ➜ nuclear charge increases ➜ atomic radius decreases

Question 7

Describe the trend of ionization energy.

Answer 7

down a group

• valence electron removed from furthest energy level ➜ less tightly held ➜ IE decreases

across a period
* stronger nuclear charge ➜ increase in attraction between outer electrons and nucleus ➜ more tightly held ➜ IE increases

Question 8

Describe trend in electron affinity.

Answer 8

• metals have low EA, non-metals have high EA
• the greater the distance between nucleus and outer energy level, the weaker the electrostatic attraction released

Question 9

Describe the trend in electronegativity.

Answer 9

• metals have low EN as they lose electrons easily
• non-metals have high EN as they gain electrons to complete the outer shell
• EN increases across a period, decreases down a group

Question 10

Describe the trends in melting points.

Answer 10

across a period

• stronger forces of attraction between the particles ➜ more energy needed to overcome forces ➜ increasing melting point until group 14
• depends on the bonding, structure, strength

Question 11

Describe the trends in metallic character.

Answer 11

• Metallic character: How easily an atom can lose electrons
• Increases down a group, decreases across a period

Question 12

Describe the trends down Group I (the alkali metals)

Answer 12

• Atomic/Ionic radius ⬆️ as there are more electron shells
• First IE ⬇️ as valence electron is further from the nucleus, easier to remove
• EN ⬇️ increased distance and shielding
• MP ⬇️ as atoms are larger, metallic bonds are weaker
• Reactivity ⬆️ as valence electrons are easier to lose due to shielding

Question 13

Describe the trends down group 7 (halogen)

Answer 13

• Atomic/Ionic radius ⬆️ as there are more electron shells
• First IE ⬇️ as valence electron is further from the nucleus, easier to remove
• EN ⬇️ increased distance and shielding
• MP ⬆️ as Van dear Waal forces becomes greater with more electrons
• Reactivity ⬇️ as attraction between nucleus and outer electrons are weaker

Question 14

Define transition metals.

Answer 14

Elements whose atoms have incomplete d-orbitals or can form positive ions with an incomplete d sub-level.

Question 15

Is zinc considered a transition element? Explain.

Answer 15

Zinc is not a transition element as it does not have an incomplete d orbital.

Question 16

Describe physical properties of transition metals.

Answer 16

• High electrical and thermal conductivity
• High MP
• High tensile strength
• Malleable
• Ductile

Question 17

Describe chemical properties of transition metals.

Answer 17

• Variable oxidation states
• Formation of complex ions
• Colored compounds
• Catalytic Behavior

Question 18

Define diamagnetic, paramagnetic, and ferromagnetic.

Answer 18

Diamagnetic

• No unpaired electrons, weakly repelled

Paramagnetic

• One or more unpaired d-orbital electrons

Ferromagnetic

• Only occurs in iron, cobalt, nickel
• Large numbers of unpaired electrons

Question 19

Define ligands.

Answer 19

Molecules or ions with a lone pair of electrons that form coordinate covalent bonds with a central metal ion.

Question 20

Define complex ions.

Answer 20

Formed when ligands dative covalently bond to a central metal ion by donating a pair of electrons

Question 21

Outline factors that affect the color of a transition metal.

Answer 21

• Nature of transition element
• Identity of metal ion
• Identity of ligand
• Oxidation state

Question 22

Describe the trends across period 3.

Answer 22

• sodium, magnesium, aluminum are metals (basic)
• aluminum oxide is amphoteric
• phosphorus and sulfur are non-metals (acidic)
• chlorine and argon are non-metals (no oxide)