H2O

Valence Electrons: the electron(s) in the outer shell of an atom’s electron cloud, which can combine with other atoms to form molecules *The number of valence electrons in an atom of an element determines many properties of that element, including the ways in which the atom can bond with other atoms.

Chemical bonds hold molecules together Chemical bonds hold molecules together . A chemical bond is a union between atoms formed when they give up, gain, or share electrons .

3 types of bonds Ionic Covalent –Non-polar –Polar Hydrogen

Ions and Ionic Bonds Ions: When an atom loses an electron, it loses a negative charge and becomes a positive ion. When an atom gains an electron, it gains a negative charge and becomes a negative ion.

Ions and Ionic Bonds •Ionic Bond: An atoms gives up or gains one or more of its electrons to another. The resulting oppositely charged ions attract one another, forming an ionic bond.

Ions and Ionic Bonds You and a friend walk past a market that sells apples for 40 cents each and pears for 50 cents each. You have 45 cents and want an apple. Your friend also has 45 cents but wants a pear.

Ions and Ionic Bonds For example, in table salt (sodium chloride) the negative chlorine ion attracts the positive sodium ion, forming an ionic bond.

Covalent Bonds A covalent bond holds together two atoms that share one or more pair of electrons Electrons in a covalent bond may be equally or unequally shared between the atoms. Non-polar covalent bond: atoms share electrons evenly Polar covalent bond: atoms share electrons unequally

Covalent Bonds Those atoms with greater positive nuclear charge pull more strongly on electrons in a covalent bond.

. For example, carbon dioxide molecule is a nonpolar molecule because of its straight-line shape. An example of a polar molecule is water because of its bent shape.

Covalent Bonds H2O (the molecule – NOT water) is a polar molecule –The (slightly) positively charged pole is around each hydrogen –The (slightly) negatively charged pole is around the oxygen

Hydrogen Bonds Hydrogen Bonds: form when partial opposite charges in different polar molecules attract each other. Polar molecules have partially charged atoms at their ends. Individual hydrogen bonds are rather weak, but collectively (together), they are quite strong.

Hydrogen Bonds The only example of Hydrogen bonding is when two or more water molecules are attracted. One water molecule can attract up to 4 other molecules.

Graphic Organizer Polar Covalent Bond Nonpolar Covalent Bond Hydrogen Bonds Feature Ionic Bond Attraction between oppositely charged ions Partial opposite charges in different polar molecules How Bond Forms Unequal sharing of electrons Equal sharing of electrons Charge on Bonded Atoms? Yes, slightly positive or slightly negative Yes; positive or negative Yes; positive or negative No H2O molecule (or other polar covalent molecule) NaCl crystal (or other ionic compound) Example Two or more H2O molecules O2 molecule