7th grade ch 1 sec 2 atoms bonding and the periodic table
TRANSCRIPT
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.
Silicon
valence electrons=
•electrons farthest from nucleus
•involved in bonding
Electron dot diagramsway of showing # valence electrons
• 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
Patterns of Valence Electrons
After the number of valence electrons reaches 8, a new period begins.
• # 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 electrons
• react with other atoms by losing valence electron
Noble gases
• Group 18
• 8 valence electrons
(except helium has 2)
• don’t react very easily with other atoms
NOBLE GASES
NOBLE GASES
Halogen family• Group 17
• 7 valence electrons
• React with other atoms by gaining 1 electron