CHAPTER 5.3

GROUPS/FAMILIES & VALENCE ELECTRONS

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

Elements in a _____ 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 ___________________

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

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

• _________ 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

Valence e’s

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 (______________):

• group _______ = the number

of valence electrons for an

element in that group.

• Valence electrons play a key role in chemical reactions.

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

OCTET RULE

• Atoms are most stable if their outer most electron shell is __________ or _____________.

• Filled shell contains ____ electrons (octet)• Except for ____ and ____ (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

_____________.

OCTET RULE

• Na has 11 protons and 11 electrons.

• Period 3 = 3 e- shells

• Group 1A = 1 Valance e-

• 2 e- in 1st shell (full)

• 8 e- in 2nd shell (full)

• 1 e- in 3rd shell (valence)

proton charge (11 x +1) = +11

+ electron charge (11 x -1) = -11

net charge = 0 (neutral)

Na

OCTET RULE

• When atoms lose or gain valence electrons _________________

• Na has 1 valence e- -- easier to _____1 than gain 7 to fulfill octet rule

• leaves only 10 electrons• (2 e- in 1st shell; 8 e- in 2nd shell; 1 e- in 3rd shell) (11 x

+1)

• (2 e- in 1st shell; 8 e- in 2nd shell; no e- in 3rd shell) + (10 x -

1)

= 1+

• Example: Cl has 7 valence e- -- easier to _______1 than lose 7

• (2 e- in 1st shell; 8 e- in 2nd shell; 7 e- in 3rd shell) (17 x +1)

• (2 e- in 1st shell; 8 e- in 2nd shell; 8 e- in 3rd shell) + (18 x -1)

= 1-

GROUPS/FAMILIESProperties

GROUP 1A – ALKALI METALS

• 1 Valence Electron.

• Soft & Silvery

• Extremely ________ (Most reactive Metals)

• Found in nature only in compounds.

• ________ found free in nature

• Mix well with water

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

Sodium reacts violently with water and releases enough energy to ignite the hydrogen gas that is produced.

Unlike most metals Sodium is soft enough to cut with a knife.

GROUP 1A – ALKALI METALS

GROUP 1A – ALKALI METALS

• Potassium (& Sodium)

• Stored under oil to keep them from reacting with the oxygen and water vapor in air.

• Cesium

• So reactive that it is usually stored in a sealed glass tube containing argon gas.

• Why argon?

GROUP 2A – ALKALINE EARTH METALS

• 2 Valence Electrons• Similar to Alkali Metals

• _____ 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• _______ found free in nature• Reactivity increases

From top to bottom

GROUP 2A – ALKALINE EARTH METALS

• Differences in reactivity among the alkaline earth metals are shown by the ways they react with _______. • No reaction occurs when beryllium is added to water.• Magnesium will react with hot water but not cold

water.• Calcium, strontium, and barium react easily with cold

water.

•Magnesium• Photosynthesis: Chlorophyll

• Creates alloys stronger yet lighter than steel

•Calcium• Oyster shell and a pearl - calcium carbonate (Ca, C, & O).

• Also found in toothpaste

• Plaster cast - calcium sulfate.

Spinach plant

Oyster shell with pearl

GROUP 3A – THE BORON FAMILY

• ____ Valence Electrons

• Most are metals

• Well-known metal – Al (aluminum)

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

• Boron is a _________

GROUP 3A – THE BORON FAMILY

• Aluminum

• Most abundant metal in Earth’s crust.

• Less reactive than Na and Mg

• Strong, lightweight, and malleable.

• Good conductor of electric current.

• Boron

• B, Si, & O form a compound used to make glass that does not shatter due to rapid temperature change. • laboratory glassware • cookware that can go directly from the oven to the refrigerator.

GROUP 4A – THE CARBON FAMILY

• ____ Valence electrons

• Family Contains

• 1 Nonmetal - C (carbon)

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

• 2 metals - Sn (Tin) & Pb (Lead)

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

GROUP 4A – THE CARBON FAMILY

• Silicon

• 2nd most abundant element in Earth’s crust.

• The clay used to produce pottery contains silicon compounds called silicates.

• Carbon• Except for water, most of the

compounds in your body contain carbon.

• Life on Earth would not exist without carbon.

• Reactions that occur in the cells of your body are controlled by carbon compounds

GROUP 5A – THE NITROGEN FAMILY

• 5 Valence electrons

• Can ______ 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 _________ properties. • Nitrogen is a gas

• Phosphorus is a solid nonmetal

• Bismuth is a dense metal.

GROUP 5A – THE NITROGEN FAMILY

• When air is cooled - O condenses before the N due to its lower boiling point

• Much of the N obtained from air is used to produce fertilizers.

• The numbers on the bags of fertilizer are, from left to right, the relative amounts of nitrogen, phosphorus, and potassium.

GROUP 6A – THE OXYGEN FAMILY

• ___ Valence electrons

• Family Contains:

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

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

• Reactive

GROUP 6A – THE OXYGEN FAMILY

• Oxygen

• Most abundant element in

Earth’s crust.

• Complex life forms need O to

stay alive because O is used to

release the energy stored in food.

• Ozone (O3) is another form of the element oxygen.

• Sulfur

• One of the first elements to be discovered because it is found in large natural deposits.

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

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

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

from Group 1A

GROUP 7A – HALOGENS• Despite their physical differences, the halogens have

similar chemical properties.• React easily with most metals.

• Image:

• Chlorine reacting with steel wool

GROUP 8A – THE NOBLE GASES

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

All Non-metalsExtremely Unreactive ________ and odorless

GROUP 8A – THE NOBLE GASES

• When electric current passes

through noble gases, they emit

different colors.

• He (Helium) emits ______,

• Ne (Neon) emits orange-red,

• Ar (Argon) emits lavender,

• Kr (Krypton) emits _______

• 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

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 of 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

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

a. True

b. False