BELL RINGER

• 1. What are the properties of metals?

• 2. What are the properties of non-metals?

CHAPTER 5.3

GROUPS/FAMILIES & VALENCE ELECTRONS

Elements in a group or “family” have similar properties.

Elements in a period have the same number of electron shells or energy levels.

VALENCE ELECTRONS

• Why do the elements in a group have similar properties?

• They have the same number of valence electrons.

• The properties are not identical because the valence electrons are in different energy levels.

• A valence electron is an electron that is in the highest occupied energy level of an atom.

• Outer most electron shell

VALENCE ELECTRONS

• Why do the elements in a group have similar properties?

N

Electrons Filling shells as atomic # increases (# of electrons goes up as # of protons goes up):

He Li Be B

Ne Na

Atomic # 1 2 3 4 5

Atomic # 7 10 11

H

1st shell nowfull, start 2nd

2nd shell nowfull, start 3rd

6

C

Valence e’s 1 2 1 2 3

4Valence e’s 5 81

VALENCE ELECTRONS

• How do we determine the number of valence electrons?

• When groups in the periodic table are labeled as Series A and Series B:

• For Series A (Groups 1A - 8A):

• group number = the number

of valence electrons

• Valence electrons play a key role in chemical reactions.

• Properties vary across a period because the number of valence electrons increases from left to right.

OCTET RULE

• Atoms are most stable if their outer most electron shell is filled or empty.

• Filled shell contains 8 electrons (octet)• Except for H and He (atomic #1 & #2)

• Atoms gain, lose, or share valence electrons in order to fill or empty their outer shell• Atoms gain, lose, or share electrons based on what is

easiest.

GROUPS/FAMILIESProperties

GROUP 1A – ALKALI METALS

• 1 Valence Electron.

• Soft & Silvery

• Extremely Reactive (Most reactive Metals)

• Found in nature only in compounds.

• NOT found free in nature

• Mix well with water

• The reactivity of alkali metals increases from the top of Group 1A to the bottom.

GROUP 2A – ALKALINE EARTH METALS

• 2 Valence Electrons• Similar to Alkali Metals

• Harder than metals in Group 1A• Higher melting points

• The melting point of magnesium is 650°C; sodium 98°C

• Almost as reactive as Alkali metals• NOT found free in nature• Reactivity increases

• From top to bottom

GROUP 3A – THE BORON FAMILY

• 3 Valence Electrons

• Most are metals

• Well-known metal – Al (aluminum)

• Less familiar metals - Ga (gallium), In (indium), and Tl (thallium).

• Boron is a metalloid

GROUP 4A – THE CARBON FAMILY

• 4 Valence electrons

• Family Contains

• 1 Nonmetal - C (carbon)

• 2 metalloids - Si (silicon) & Ge (germanium)

• 2 metals - Sn (Tin) & Pb (Lead)

• Notice that the metallic nature of the elements increases from top to bottom within the group. Germanium is a better conductor of electric current than silicon.

GROUP 5A – THE NITROGEN FAMILY

• 5 Valence electrons

• Can share electrons to form compounds

• Family Contains:• 2 nonmetals - N (nitrogen) & P (phosphorus)

• 2 metalloids - As (arsenic) & Sb (antimony)

• 1 metal - Bi (bismuth).

• Group 5A includes elements with a wide range of physical properties. • Nitrogen is a gas

• Phosphorus is a solid nonmetal

• Bismuth is a dense metal.

GROUP 6A – THE OXYGEN FAMILY

• 6 Valence electrons

• Family Contains:

• 3 nonmetals - O (oxygen), S (sulfur), & Se (selenium)

• 2 metalloids - Te (tellurium) & Po (polonium)

• Reactive

GROUP 7A – HALOGENS• 7 Valence electrons• All Nonmetals• At room temperature:

• chlorine is a gas, • bromine is a liquid• iodine is a solid.

• MOST Reactive of the nonmetals• Often find these elements bonded with elements

from Group 1A

GROUP 8A – THE NOBLE GASES

8 Valence electrons = Full Shell – Octet RuleHelium (He) has only 2 valence electrons = Full

All Non-metalsExtremely Unreactive Colorless and odorless

GROUP 8A – THE NOBLE GASES

• When electric current passes

through noble gases, they emit

different colors.

• He (Helium) emits pink,

• Ne (Neon) emits orange-red,

• Ar (Argon) emits lavender,

• Kr (Krypton) emits white

• Xe (Xenon) emits blue.

ASSESSMENT QUESTION

1. Why do elements in a group have similar chemical properties?

a. They have the same number of valence electrons.

b. They have the same ratio of protons to neutrons.

c. Their atomic masses are multiples of the least massive element of the group.

d. They have the same number of total electrons.

ASSESSMENT QUESTION

1. Why do elements in a group have similar chemical properties?

a. They have the same number of valence electrons.

b. They have the same ratio of protons to neutrons.

c. Their atomic masses are multiples of the least massive element of the group.

d. They have the same number of total electrons.

ASSESSMENT QUESTION

2. Which Group 2A element would you expect to react most readily with water?a. beryllium (Be)b. calcium (Ca)c. barium (Ba)d. radium (Ra)

ASSESSMENT QUESTION

2. Which Group 2A element would you expect to react most readily with water?a. beryllium (Be)b. calcium (Ca)c. barium (Ba)d. radium (Ra)

ASSESSMENT QUESTION

3. In general, the metallic characteristics within a period decreases from left to right.

a. True

b. False

ASSESSMENT QUESTION

3. In general, the metallic characteristics within a period decreases from left to right.

a. True

b. False

ASSESSMENT QUESTION

4. Elements of the Nitrogen Family have

a. 4 Valence electrons

b. 6 Valence electrons

c. 5 Valence electrons

d. 7 Valence electrons

ASSESSMENT QUESTION

4. Elements of the Nitrogen Family have

a. 4 Valence electrons

b. 6 Valence electrons

c. 5 Valence electrons

d. 7 Valence electrons

ASSESSMENT QUESTION

5. Atoms are least stable if their outer most electron shell is filled or empty.

a. True

b. False

ASSESSMENT QUESTION

5. Atoms are least stable if their outer most electron shell is filled or empty.

a. True

b. False