Transcript Chemistry of Life

Chemistry of Life
Element
 A substance that cannot be broken down into
simpler substances.
 Each element is identified by a one or two
letter symbol.


Ca = Calcium
C = Carbon
 Trace Element

Present in living things in very small amounts.
Atom
 Smallest particle of an element that has all
the characteristics of that element.
Structure of the Atom
 Nucleus

Protons (positive)
Each element has a different number of protons.
 The number of protons determines the characteristics of
each element
 Determines the atomic number.


Neutrons (neutral)

Atomic mass – atomic number = average number of
neutrons
Structure of the Atom
 Electron Cloud

Electrons (negative)
Electrons surround the nucleus because of the
attraction between the opposite charges.
 All the electrons occupy distinct energy levels.

Structure of the Atom
 All atoms have the same number of protons
and electrons, so the atoms have a neutral
charge.
Isotope
 Atoms of the same element which vary in the
number of neutrons they contain are called
isotopes.
 Isotopes are named by the total number of
neutrons and protons in the atom.

Example: Carbon-12 and Carbon-14
 Some isotopes can be radioactive.
Compound
 A substance composed of atoms of two or
more different elements that are chemically
combined.
 Atoms combine with other atoms only when
the resulting compound is more stable than the
individual atoms.
 Atoms become stable when their outermost
energy level is full.
How do atoms fill their outermost
energy level?
 Form a covalent bond and share their
electrons with another atom.

A molecule is a group of atoms held together by
covalent bonds.
How do atoms fill their outermost
energy level?
 Form ions by giving away electrons or take
electrons from other atoms.


When atoms do this they gain either a positive or
a negative charge.
Ions with opposite charges can form compounds
through ionic bonding.
Chemical Reactions
 Occur when bonds are formed or broken,
causing substances to recombine into different
substances.
 The substances that undergo the chemical
reactions are called the reactants.
 The substances formed by the chemical
reaction are called the products.
Chemical Reactions
 The substance created by a chemical reaction
has different properties than the reactants that
formed it.
 Atoms are never created or destroyed in
chemical reactions, but simply rearranged.
 Represented by writing chemical equations.
Chemical Reactions
 In organisms, chemical reactions occur inside
cells.

All the chemical reactions occurring within an
organism are referred to as the organism’s
metabolism.
Mixture
 A combination of substances in which the
individual components retain their own
properties.
 A solution is a mixture in which one or more
substances (solutes) are distributed evenly in
another substance (solvent).
 The more solute dissolved in a solvent, the
greater the concentration of the solution.
pH
 A measure of how acidic or basic a solution
is.
 Measured on a scale of 0 to 14.
 A substance with a pH of 7 is considered
neutral.
Acid
 Any substance that forms hydrogen (H+)
ions in water.
 pH below 7.
Base
 Any substance which forms hydroxide ions
(OH-) in water.
 pH above 7.