PERIODIC TRENDS!!

VALENCE ELECTRONS Valence electrons: Electrons in the

highest energy level

These electrons are the ones that bond!! The group A # matches how many

valence electrons

VALENCE ELECTRONS

Group # # of valence electrons

1 or 1A 1

2 or 2A 2

13 or 3A 3

14 or 4A 4

15 or 5A 5

16 or 6A 6

17 or 7A 7

18 or 8A 8

Group 13-18. # of valence electrons equal to group number - 10

YOU CAN PREDICT THE CHARGE OF THE IONS

Octet rule: atoms will gain or lose electrons to have a full energy level (8 electrons)

Period number responds to how many energy levels an atom has

PREDICTING CHARGES OF IONS

ION SIZE TRENDS

ION: an atom that lost or gained electrons Cation: metal atom that loses e- (+) Anion: nonmetal atom that gain e- (-)

ALL CATS HAVE PAWS (AND ARE MEAN)

(cation is positive: metals)

PERIODIC TRENDS

There are 4 trends of the periodic table you will need to know Ionic Size Atomic Size

Electronegativity

Ionization Energy

Need to know how AND why they trend the way they do.

1. IONIC SIZE TRENDS

Cations are smaller than their neutral

atoms

Because they lost an electron and energy

level Anions are larger than their neutral

atoms Because they gain electrons (which repulse

one another)

IONIC SIZE EXAMPLE

Ex 1: Which is larger? Mg or Mg2+

Ans: Mg Ex 2: Which is larger?

S or S2-

Ans: S2-

2. ATOMIC SIZE

The size of the atom

2. ATOMIC SIZE

Atomic size increases as you move: from right to left in a period from top to bottom in a group Francium has the largest size

Fr

ATOMIC SIZE REASON

Going from Left to Right Gets smaller because you add more

protons to nucleus and then pull in the electrons

Going Down Gets larger because you add energies

ATOMIC SIZE EXAMPLE

Ex. 1: Arrange the following elements in order of their decreasing size. P(15), Mg(12), S(16)

Ans: Mg,P, S

3. ELECTRONEGATIVITY TRENDS

Electronegativity is a measure of the

ability of an atom to attract electrons

from another atom

ELECTRONEGATIVITY TRENDS

Electronegativity increases as you move: from left to right across a period from bottom to top in a group

Fluorine (9) is the most electronegative element

F

ELECTRONEGATIVITY REASON

Electronegativity is opposite of atomic size, because the smaller the atom…the more electrons are attracted to the nucleus

TRENDS IN ELECTRONEGATIVITY

Why are the noble gases not on here??!

ELECTRONEGATIVITY EXAMPLE

Arrange the following in order of their increasing electronegativity. Rb(37), I(53), Sn(50)

Ans: Rb, Sn, I

4. IONIZATION ENERGY TRENDS

The ionization energy is the energy

needed to remove an electron from a

gaseous atom.

The higher ionization energy, the harder it

is to pull off electrons

IONIZATION ENERGY TRENDS

Ionization energy increases as you move: from left to right across a period from bottom to top in a group

Helium (2) has the highest ionization energy

He

IONIZATION ENERGY

Reason: The smaller the atom, the closer electrons are to nucleus so higher the ionization energy

IONIZATION ENERGY EXAMPLE

Arrange the following in order of increasing ionization energy. He(2), Xe(54), Ar(18)

Ans: Xe, Ar, He

PERIODIC TRENDS SUMMARY

METAL REACTIVITY TRENDS Metal reactivity increases as you

move: right to left across a period top to bottom in a group

Francium (87) is the most reactive metal

Fr

NON-METAL REACTIVITY TRENDS

Non-metal reactivity increases as you move: left to right across a period bottom to top in a group

Fluorine (9) is the most reactive non-metal

F

REACTIVITY EXAMPLES

Ex. 1: Which is more reactive? Fe(26) or Co(27) Ans: Fe

Ex. 2: Which is less reactive? Cl(17) or F(9) Ans: Cl