Chemistry of Life:Chemistry of Life:Atoms, Ions, Molecules, Atoms, Ions, Molecules,

and Waterand Water

August 13 & 14

Lecture and Lab Rotations

AtomsAtoms MatterMatter- any substance that has mass - any substance that has mass Matter is composed of small particles called Matter is composed of small particles called atomsatoms. .

Difference between mass and weight:Mass refers to the amount of a substance, whereas weight refers to the force of gravity on the substance. EX: walking on the moon

Example of an atom: CarbonExample of an atom: Carbon

Carbon is an essential atom for life.Carbon is an essential atom for life. It can assemble into DNA, proteins, It can assemble into DNA, proteins,

carbohydrates and lipids, making carbohydrates and lipids, making complex life possible. complex life possible.

CarbonCarbon

Atomic massAtomic mass is the number of protons and is the number of protons and neutrons in the nucleus of the atom. Carbon neutrons in the nucleus of the atom. Carbon is is 1212..

Atomic numberAtomic number is the number of protons in is the number of protons in the nucleus. Carbon is the nucleus. Carbon is 66. .

Carbon is a Carbon is a neutral atomneutral atom. .

ElementElement

Atoms with the same atomic number Atoms with the same atomic number (same number of protons) have the (same number of protons) have the same chemical properties and belong same chemical properties and belong to the same to the same element.element.

Energy: the ability to do Energy: the ability to do workwork

Electrons are negatively charged and carry Electrons are negatively charged and carry the ability to be attracted to the positively the ability to be attracted to the positively charged nucleus, and repelled by the charged nucleus, and repelled by the negative charge of other electrons.negative charge of other electrons.

When an When an electron moves electron moves toward the toward the nucleus it releases nucleus it releases energy, and energy, and absorbs energy absorbs energy when it moves when it moves away from the away from the nucleus. nucleus.

Electron ShellsElectron Shells Electron shells Electron shells are where the energy of the are where the energy of the

atom is stored. atom is stored. OrbitalOrbital is the volume of space around a nucleus is the volume of space around a nucleus

where an electron is most likely to be found. Each where an electron is most likely to be found. Each electron shell has a specific number of orbitals, electron shell has a specific number of orbitals, and each orbital can only hold up to two and each orbital can only hold up to two electrons. electrons.

Since carbon has 6 electrons, how many shells (and electrons on each shell) does it have?

IonsIons An atom can gain or loose electrons from its outer An atom can gain or loose electrons from its outer

shell. shell. An An ionion is when the number of electrons and the is when the number of electrons and the

number of protons is not equal because the atom number of protons is not equal because the atom has gained or lost an electron.has gained or lost an electron.

A sodium atom becomes a sodium ion when it looses an electron because the nucleus is left unbalanced and becomes positively charged.

IsotopesIsotopes

An An isotopeisotope is an atom that has the is an atom that has the same number of protons but different same number of protons but different number of neutrons.number of neutrons.

The number of neutrons in an atom of The number of neutrons in an atom of a particular element can vary without a particular element can vary without changing the properties of the changing the properties of the element.element.

Isotopes have the same atomic Isotopes have the same atomic number, but different atomic mass. number, but different atomic mass.

MoleculesMolecules A A moleculemolecule is a group of atoms held is a group of atoms held

together by energy.together by energy. A A chemical bondchemical bond is the energy or is the energy or

force that holds two atoms together. force that holds two atoms together.

Ionic BondIonic Bond

When atoms are attracted to each When atoms are attracted to each other by opposite electrical charges.other by opposite electrical charges.

2 key properties: strong and non-2 key properties: strong and non-directionaldirectional

Covalent BondCovalent Bond A strong chemical bond when that forms between two A strong chemical bond when that forms between two

atoms when they share electrons. atoms when they share electrons. Why do atoms in molecules share electrons?Why do atoms in molecules share electrons?

Single, double (two pairs of electrons are shared), triple Single, double (two pairs of electrons are shared), triple covalent bonds.covalent bonds.

Carbon has 4 electrons in outer shell and can form as many Carbon has 4 electrons in outer shell and can form as many as 4 covalent bonds. as 4 covalent bonds.

Hydrogen BondsHydrogen Bonds

Form when the positive end Form when the positive end of one polar molecule is of one polar molecule is attracted to the negative attracted to the negative end of another polar end of another polar molecule.molecule.

Are weak chemical bonds Are weak chemical bonds and one nucleus may be and one nucleus may be better at attracting the better at attracting the shared electron than the shared electron than the other and spend more time other and spend more time in the vicinity of the more in the vicinity of the more strongly attracted atom. strongly attracted atom.

Characteristics: highly Characteristics: highly directional and create tight directional and create tight bonds through the effect of bonds through the effect of many weak interactions. many weak interactions.

Hydrogen bonds give water Hydrogen bonds give water unique properties:unique properties:

Heat storage-Heat storage- it takes water a long time to it takes water a long time to boil and coolboil and cool

Ice formation-Ice formation- Why is ice less dense than Why is ice less dense than water?water?

High heat of vaporization-High heat of vaporization- water can water can evaporateevaporate

CohesionCohesion (ability to bind to other polar (ability to bind to other polar molecules that are water; when this polar molecules that are water; when this polar

substance is not water, it is adhesion)substance is not water, it is adhesion) High polarity-High polarity- hydrophilic and hydrophilic and

hydrophobic hydrophobic