H 2 O.
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.
A chemical bond is a union between atoms formed when they give up, gain, or share electrons .
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.
When an atom loses an electron, it loses a negative charge and become a positive ion. When an atom gains an electron, it gains a negative charge and becomes a negative ion.
•An atoms gives up or gains 1 or more of its electrons to another.
•The resulting oppositely charged ions attract one another, forming an ionic bond.
Those atoms with greater positive nuclear charge pull more strongly on electrons in a covalent bond.
A carbon dioxide molecule is a nonpolar molecule because of its straight-line shape. In contrast, a water molecule is a polar molecule because of its bent shape.
H2O is a polar molecule
–The (slightly) positively charged pole is around each hydrogen
–The (slightly) negatively charged pole is around the oxygen
Polar Covalent Bond
Nonpolar Covalent Bond
Attraction between positive ions and surrounding electrons.
Attraction between oppositely charged ions
How Bond Forms
Equal sharing of electrons
Unequal sharing of electrons
Charge on Bonded Atoms?
Yes, slightly positive or slightly negative
Yes; positive or negative
H2O molecule (or other polar covalent molecule)
NaCl crystal (or other ionic compound)
Calcium (or other metal)