CH. 1SEC. 2

ATOMS, BONDING & THE PERIODIC

TABLE

Silicon has 14 electrons. The 4 electrons that orbit the nucleus

in the outermost "valence" energy level are given to, accepted from, or

shared with other atoms.

SiliconSi

valence electrons=

•electrons farthest from nucleus

•involved in bonding

electron dot diagram (Lewis dot structure)

•way of showing # valence electrons

Patterns of Valence Electrons

After the number of valence electrons reaches 8, a new period begins.

• Much like people, most atoms don't like to live solitary existences.

• They need to COME TOGETHER with other atoms to lead more stable, happier lives.

• This process of coming together is called chemical bonding.

chemical bond• force that holds atoms together

• electrons may be transferred from one atom to another, or they may be shared between atoms

• # of protons in nucleus

–elements arranged in order of increasing atomic #

atomic number

• group (family) = column (up & down)

• period = row

alkali metals• Group 1

• 1 valence electron

• react w/ other atoms by losing valence electron

halogen family• Group 17• 7 valence

electrons• react w/ other

atoms by gaining 1 electron

noble gases• Group 18

• 8 valence electrons

(except helium has 2)

• don’t react very easily with other atoms

NOBLE GASES

YouTube video-Periodic Table