Phys. Science 4-2: Types of Bonds

Describe Ions and how they form

Distinguish between Ionic, Covalent, and Metallic Bonds

Predict what sort of bond will form based on the types of elements involved

There are three different types of bonds that can form between elements

• Ionic

• Covalent

• Metallic

Recall: Electrons have a negative charge, and protons have a positive charge

• Normally, the two are balanced in an atom, and it is neutral

When atoms are exposed to enough energy, they can gain or lose electrons

Ion: A charged particle that forms when an atom or group of atoms gains or loses one or more electrons

• ions can be positive or negative, depending on whether they gain or lose electrons

  • Ions take the shortest route to having a filled shell

    • It is easier to lose one or two electrons than to gain 7 or 6

Ionic Bonds: The attractive force between oppositely charged ions, which form when electrons are transferred from one atom to another

• One atom is "stronger" than the other and takes electron(s) from it, dragging the rest of the atom along with it

  • Takes electrons until it has a full outer energy level with 8 electrons

Ionic Bonds create Ionic Compounds

Positive charges form when an atom loses an electron

• It now has more protons than electrons and is positively charged

Cation: A positively charged ion

• In General, Metals lose electrons and form cations

Forming cations requires energy to lose the electrons

The electrons that metals lose have to go somewhere

Nonmetals will pick up the electrons and use them to fill their outermost energy level

• Now have more electrons, so they have a negative charge

Anions: Ions that have a negative charge due to having more electrons than protons

In General, Nonmetals form anions

• When an atom becomes an anion, we change the name so the element name ends with -ide

  • Chloride, Bromide, Oxide

Ionic Compounds form when positive cations are attracted to negative anions

• A cation is able to give enough electrons to fill the outer energy level of the anion

• The ending compound is neutral because the positive and negative charges cancel out

Ionic compounds only form between a metal and a nonmetal

Ionic Compounds form hard solids called crystals

• Have flat faces and straight edges

Crystal Lattice: The regular pattern in which a crystal is arranged

• Positive and negative ions form a repeating Three-Dimensional shape

Ionic Compounds are Brittle

Ionic Compounds have high Melting points and dissolve in water

• When dissolved, they can conduct Electricity

Metals can form bonds with other metals

Metallic Bond: A bond formed by the attraction between positively charged metal ions and the electrons around them

• Metal atoms can move close enough together that their electron energy levels overlap, allowing electrons to travel from atom to atom

• Give metals their unique properties

  • shiny

  • Able to conduct heat and electricity through the movement of electrons

  • Ductile and Malleable

Covalent Bond: A bond formed when atoms share one or more pairs of electrons

• Atoms merge close enough that they can share the electrons equally between their outermost energy level

Form between the atoms of Nonmetals

Molecule: A group of atoms that are held together by chemical forces

• The smallest unit of matter that can exist by itself and retain all of a substance's chemical properties

Molecules contain at least two atoms bonded by a covalent bond

Most molecules are made of two or more elements, but some are made of two of the same element

Diatomic Molecule: a molecule bonded by two of the same element

• Mainly Halogens

• Oxygen

• Nitrogen

Atoms can share one or more pairs of electrons at a time

• More complicated molecules share more pairs of electrons

Carbon is a unique atom because of its four valence electrons

• Allows it to form four covalent bonds and make many complex molecules with different shapes

Most covalently bonded substances have: Low Melting/Boiling Points

• Water is a major exception

Many (But not all!!) are gases at room temperature

Covalent solids tend to be soft