HS

Chemistry Unit 3 Study Guide

Ionics

Ions

Metals ALWAYS form cations (+) because they lose electrons

  • Cation —> t —> +

Nonmetals form anions (—) because they gain electrons

  • Anion —> n —> negative —> —

Every element wants a noble gas configuration

Compounds are ALWAYS neutral

Transition Metals

Most can have multiple charges because they can have multiple valence electrons. Exceptions are shown in table

Use Roman Numerals to indicate charge

  • Fe (II) or Mn(VI)

Lewis Dot Structure

Shows the transfer of electrons between Metals and Nonmetals

Formula Writing

If you know name, use the steps to find the formula. If you know formula, work backwards.

  1. Write element symbols

  2. Write charges

  3. Swap, drop, and make positive

  4. Factor

Polyatomics

These are compounds that behave like elements. Use “( )“ to indicate the number of polyatomics

Naming Ionics

  1. Name the cations first (positive charge)

  2. Name the anion.

    a. If polyatomic, just put it as it is

    b. If element, change ending to -ide

  3. If cation is a transition metal, add roman numerals.

Covalent

Between at least 2 nonmetal elements

Lewis Dot Structure

Shows valence electrons, but they are shared!

  1. Count total valence electrons

  2. Least electronegative atom goes in the center. This is the central Atom (CN)

  3. Place all other atoms around it symmetrically

  4. Bond each element to CN. Each bond (—) is 2 electrons

  5. Subtract # of electrons from total

  6. Place remaining electrons on outer elements. Any left over go to CN

  7. Check for octets. If there is not an octet, manipulate electrons to make it work

Notes:

  • Hydrogen doesn’t have octet as it can only do 1 bond

  • Be can do 2 bonds max

  • B can do 3 bonds max

  • C always has 4 bonds, is always the central atom, and has no lone pairs

  • Some elements in Period 3 and down can have bigger octets (P, S, Se, I, Xe)

  • O prefers double bonds

  • N prefers triple bonds

  • In bonding “:“ and “—“ are the same thing

Formula Writing

  1. Add symbols used in name

  2. Add numbers based on suffixes

Naming Covalent

  1. Name 1 element and add -ide to 2nd element

  2. Add prefixes as necessary

    • 1st element doesn’t get mono- suffix

    • don’t do o-o, a-o, a-a, o-a

    • remove vowels at the end of suffix if necessary

1—Mono 3—Tri 5—Penta 7—Hepta 9—Nona

2—Di 4—Tetra 6—Hexa 8—Octa 10—Deca

VSEPR Theory

Valence Shell Electron Pair Repulsion Theory

Predicts the shape of 3d molecules by using the fact that electrons regions (bonded pairs or lone pairs) push other electron regions away

mind the page break

Polarity

When there is an unequal sharing because 1 atom has a stronger charge than another side

Bond Polarity

Based on EN vales

Non-polar bonds: electrons are equally shared because they are the same element

Polar bonds: electrons are unequally shared because they are different elements

Molecular Polarity

Nonpolar:There are no lone pairs on CN AND all the elements around CN are the same

Polar: There is a lone pair on CN OR different elements surround CN