How to Bond-Atoms bond when their valence electrons interact

-Atoms join to form bonds so that each atom has a stable electron configuration.

-When this happens, each atom has an electronic structure similar to that of a noble gas.

-Two basic kinds of chemical bonding: ionic bonding and covalent bonding

Ionic Covalent

Structure Network of bonded ions Molecules

Valence electrons Transferred Shared

Electrical conductivity Good when melted or dissolved

Poor

Sate at room temp Solid Solid, liquid or gas

Melting and boiling points

high low

What are ions?!

Ionic BondsIonic bonds form when ions are created. Atoms of

metals form positively charged ions. Atoms of nonmetals form negatively charged ions.   

Ionic bonds are formed by the transfer of electrons.

One of the atoms gains the electrons that the other one loses. The result is a positive ion and a negative ion.

SALT!Each positive Na ion attracts a lot of negative Cl ions and

vise versa. Two atoms like to form an ionic bond when one atom has more attraction for electrons than the other. Cl has much more attraction for electrons than Na. So, neutral Cl atoms react with neutral Na atoms to form sodium chloride.

Think of this…

One little boy atom really wants to impress a little girl atom.

He gives her a gift (an electron). Since he gave up this gift (electron) he is really happy about it, he is a positive ion.

She gets the gift (electron), but realizes it’s a really bad gift. She is negative ion.

We put the FORM in FormulaIonic compounds are in the form of

networks, not molecules- there is no molecule of NaCl. Every Na atom sits next to 6 Cl atoms.

So what is there?!Salt’s chemical formula, NaCl, tells us that there is one Na+ ion for every Cl− ion, or a 1:1 ratio of ions. Thus, the compound has a total charge of zero. One Na+ ion and one Cl− ion make up a formula unit of NaCl.

Different compounds can have different ratios

When dissolved in water, ionic compounds conduct electricity.

Electric current is moving charges. Solid ionic compounds do not conduct electric current because the charged ions are locked into place. But if you dissolve it in water or melt it, it can conduct electric current. This is because the ions are then free to move.

Covalent BondsAtoms joined by covalent bonds share

electrons. Compounds that are made of molecules,

have covalent bonds.Covalent bonds usually form between

nonmetal atoms.Covalent compounds can be solids, liquids,

or gases. They have low melting points, molecules are

free to move when the compound is dissolved or melted- do not conduct electricity, because they are not charged.

Think of this…

Two little atoms go to a party, both bring cupcakes.

The decide to share their cupcakes.

Since the cupcakes are equally good, neither atom is positive or negative… they are neutral.

How strong are your bonds?Each line between 2

atoms represents a pair of shared

electrons. 1 line would

represent 1 pair, 2 lines= 2 pairs… and so on.

Each addition of a line makes the bonds stronger, but also shorter.

Didn’t your mother teach you how to share?!

When atoms of the same element bond, electrons are equally attracted to the positive nucleus of each atom. Bonds where electrons are shared equally are called nonpolar covalent bonds.

When two atoms of different elements share electrons, the electrons are not shared equally. The shared electrons are attracted to the nucleus of one atom more than to the nucleus of the other. An unequal sharing of electrons forms a polar covalent bond.

Usually, electrons are more attracted to atoms of elements that are located farther to the right and closer to the top of the periodic table.

Electrons “metal-ing” in your life? Metals can conduct electricity when they are solid.

What are other properties of metals?!

Why… because their atoms and electrons can move freely throughout a metal’s closely packed structure.

The atoms in metals such as copper form metallic bonds. The attraction between an atom’s nucleus and a neighboring atom’s electrons packs the atoms together. This packing causes the outermost energy levels of the atoms to overlap, so electrons are free to move from atom to atom.