Lesson 3 - Trends in the Periodic Table

Question 1

Atomic radius

Answer 1

is the distance from the nucleus to just beyond the outermost electrons (valence electrons)

Question 2

Within a period … The # of energy levels stays the…

Answer 2

same

Question 2

Within a group… The # of Valence e- stays the…

Answer 2

same

Question 3

Atomic radius: Left-to-right in a period:

Answer 3

More protons in the nucleus for same number of energy levels = the ENC increases, stronger attraction between nucleus and electrons = smaller atomic radius

Question 4

Atomic radius: Top-to-bottom in a group:

Answer 4

Number of energy levels increases = weaker attractive force due to increasing number of shielding electrons = larger atomic radius

Question 5

How atomic radius works

Answer 5

effective nuclear charge, which is the net force experienced by an electron in an atom due to the positively charged nucleus

Question 6

Arrange Xe,Rb,Sr in largest to smallest atomic radius

Answer 6

Rb, Sr, Xe

Question 7

Ionic radius

Answer 7

Size of atom after ion formation depends on whether a cation (+) or anion (-) was formed

Question 8

Cations are always_____ than their original neutral atoms

Answer 8

smaller

Cation has one less energy level than the neutral atom
The same ENC is now shared among less electrons, so force is slightly higher on each one; nucleus pulls the electrons more closely

Question 9

Anions are always_____ than their original neutral atoms

Answer 9

bigger

The same ENC is now shared among more electrons, so force is slightly weaker on each one; nucleus cannot hold electrons quite so close

Question 10

Ionization Energy

Answer 10

Ionization energy is the amount of energy required to remove an electron from an atom or ion in the gaseous state

Question 11

What does the amount of energy used for ionization energy depends on what?

Answer 11

on which electron is being removed

Question 12

Ionization Energy repped in a equation

Answer 12

X (g) + energy —> X+ (g) + e-

Question 13

Ionization Energy left-to-right across a period

Answer 13

increase

ENC increases, so valence electrons are more strongly attracted to the nucleus, and thus more energy is required to remove an electron from the atom

Question 14

Ionization Energy top-to-bottom in a group

Answer 14

decrease

Atomic radius increases, so the attraction between the valence electrons and nucleus becomes weaker, and thus less energy is required to remove the first valence electron

Question 15

Explain which would have a higher ionization energy; sodium or rubidium?

Answer 15

Sodium as they are in the samw group and decreasing.

-Atomic radious is increasing so the attractive forces between the valence electrons and nucles become wekaing thus less energy is need to remove the valence e-

Question 16

Electron affinity

Answer 16

Electron affinity is the energy change that occurs when an electron is accepted by an atom in the gaseous state

-When an electron is added to a neutral atom in the gaseous state, energy is usually released

Question 17

Electron affinity repped as a equation

Answer 17

X(g) + e- –> X+(g) + Energy

Question 18

Electron affinity can also be thougth as

Answer 18

as the amount of energy an atom (or ion) is willing to pay to buy another electron

Question 19

Electron affinity top-to-bottom in a group

Answer 19

decreases

Atomic radius increases, so there is a weaker attractive force between the nucleus of atom and the new electron, and thus the atom is less willing to spend energy to add an electron

Question 20

Electron affinity left-to-right across a period

Answer 20

increases

ENC increases, so the force of attraction between the nucleus and the valence electrons increases, and thus the atom is more willing to spend energy to add an electron

HOWEVER Noble gases are an exception!

Question 21

Which element in each of the following pairs will have a lower electron affinity?

A) S or Se

Answer 21

Se

as when you go down a group electron affinity decreases because the atomic raidus increases so there is a weaker force of attarction between valence e- and nucles so the atom is less willing to spend enegery for new e-

Question 22

Electronegativity

Answer 22

a way of quantitatively describing the ability of an atom to attract electrons when bonded, combining ionization energies, electron affinity, and some other measures of reactivity

-Linus Pauling came up with this

Question 23

What element did he assign the value 4.0 to F and why?

Answer 23

assigned a value of 4.0 to fluorine, the element considered to have the greatest ability to attract electrons within a chemical bond

Question 24

TRUE OR FALSE: , electronegativity IS a measurement

Answer 24

FALSE:

electronegativity is NOT a measurement

Question 25

Electronegativity generally _____ top-to-bottom in a group

Answer 25

decreases

Atomic radius increases, so there is a weaker attractive force between the nucleus of atom and the new electron, and thus the atom is less willing to spend energy to add an electron

Question 26

Electronegativity _______ left-to-right across a period

Answer 26

increases

ENC increases, so the force of attraction between the nucleus and the valence electrons increases, and thus the atom is more willing to spend energy to add an electron

Question 27

Reactivity

Answer 27

Non-metal increasing as it moves form bottom left corner diagnoall across to top right corner

Metlaocs decreases as you go from top rigth corner to bottom left corner

Question 28

Metallic Reactivity: Reactivity _____ top-to-bottom in a group

Answer 28

increases

ENC stays the same, more electrons are added to farther shells = less hold on electrons 🡪 allows metals to readily give up electrons

Question 29

Metallic Reactivity: Reactivity _____ left-to-right in a period

Answer 29

decreases

ENC increases, electrons are added to same shell and held tightly = more difficult for metals to give away electron

Question 30

Non-Metallic Reactivity: Reactivity ___ top-to-bottom in a group

Answer 30

decreases

ENC stays the same, more electrons are added to farther shells = less hold on electrons 🡪 harder for non-metals to gain an electron

Question 31

Reactivity _____left-to-right in a period

Answer 31

increases

ENC increases, electrons are added to same shell and since electronegativity increases across a period, non-metals will react to gain electrons

Question 32

The most reactive metals are the ______ since they are the best electron givers.

Answer 32

largest

Question 33

The most reactive nonmetals are the _____ ones, the best electron takers.

Answer 33

smallest