CHEMISTRY OF LIFE Section 1Section 4 The nature of matter Energy and Chemical Reactions Section 2 Importance of water Section 3 Organic molecules

Section 1: Nature of Matter Atoms Atoms: the smallest unit of matter that can not be broken down by chemical means Atoms consist of three different particles: protons, neutrons, and electrons

Protons/Neutrons Protons and neutrons make up the nucleus of an atom Proton have a positive (+) charge Neutrons have no charge (o) ◦ Protons = positive ◦ Neutrons = neutral

Electrons Electrons have a negative (-) charge Electrons are flying around the nucleus ◦ not directly attached to anything

Atoms have equal numbers of protons and electrons ◦ Atoms are neutral, no net charge ◦ Because the # of protons = the # of electrons Atoms are the smallest unit of matter that can not be broken down ◦ Protons, neutrons, electrons

Elements Element – is a pure substance made only of one kind of atom ◦ Aluminum is only made of aluminum

Elements What is the chemical formula for water? ◦H20◦H20 ◦ Is water an element? Salt – sodium and chlorine (NaCl) ◦ One atom of sodium and one atom of chlorine C 6 H 12 O 6 ◦ Sugar!

Elements Atomic # is # of protons ◦ (# of protons = # of electrons) Atomic weight Symbol

Elements Isotopes Isotope – when the number of protons does not equal the number of neutrons Carbon has 6 protons and 6 electron Carbon 14 isotope has 6 protons and 8 electrons

Bonding Aluminum is only aluminum atoms and water is hydrogen and oxygen atoms How do they stay together? ◦ Through bonding! Three types of bonds ◦ Hydrogen, Covalent, Ionic

Covalent Bonds Form when two or more atoms share electrons to form a molecule Unlike hydrogen bonds ◦ Covalent bonds deal with electrons

Covalent Bonds H 2 0 So the hydrogen atoms share electrons with the oxygen atom. Hydrogen and oxygen co-operate (covalent) and share electrons to make a water molecule

Hydrogen Bonds A weak chemical attraction between polar molecules Water is a polar molecule ◦ Water forms hydrogen bonds

Hydrogen Bonds Water forms hydrogen bonds The positive hydrogen molecules are attracted to the neighboring negative oxygen molecules Forms weak hydrogen bonds

Ionic Bonds Dealing with electrons Not as “friendly” when ionic bonds are formed Ionic bonds – formed when an atom gains or loses an electron Remember, a normal atom has no charge ◦ So there is no attraction one way or the other

Ionic Bonds The atom that loses the electron now has a (+) charge ◦ Because it still has the same # of protons (+) but fewer electrons (-) ◦ Now the atom is not balanced and has more protons than electrons, giving it a positive charge The atom that gains the electron now has a negative (-) charge ◦ Still same # of protons (+), but more electrons (-) now ◦ So more electrons than protons results in a negative charge So a positive and a negative attract = ionic bond Na had 11 protons and 11 electrons Cl has 17 protons and 17 electrons Na has 11 protons and 10 electrons Cl has 17 protons and 18 electrons