Chemistry Chapter 3

• elements in the same horizontal row
• same number of energy shells

• elements in the same vertical column
• same number of valence electrons

• alkali metals
• 1 valence electron

• alkali earth metals
• 2 valence electrons

• halogens
• 7 valence electrons

• noble gases
• 8 valence electrons

Group 3-12

• location and energy of electrons around a nucleus (n)
• > n = > energies/distances

• each shell made up of one or more subshells
• s, p, d, f
• number of subshells = number of the shell (shell 3 contains 3s, 3p, 3d)
• identify shell by shell #, subshell letter (3p subshell)

• specific volumes of space around the nucleus where electrons move
• s subshell - 1 orbital - 2 electrons
• p subshell - 3 orbitals - 6 electrons
• d subshell - 5 orbitals - 10 electrons
• f subshell - 7 orbitals - 14 electrons
• Two electrons per orbital

1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 5s, 4d, 5p, 6s, 4f, 5d, 6p, 7s, 5f, 6d

Gallium 31 electrons 1s²2s²2p⁶3s²3p⁶4s²3d¹⁰4p¹

Electronic configurations of noble gases end with completely filled s and p subshells

• He: 1s²
• Ne: [He]2s²2p⁶
• Ar: [Ne]3s²3p⁶
• Kr: [Ar]4s²4p⁶
• Xe: [Kr]5s²5p⁶

Example: Mg -> [Ne]3s²

• elements become less metallic left to right across periods
• elements become more metallic top to bottom down group

• elements become smaller left to right across periods
• elements become larger top to bottom down group

atom or molecule where electrons do not equal protons (net positive or negative charge)

• positive charge
• has lost electrons
• metals

• negative charge
• has gained electrons
• nonmetals