Anything that occupies space and has mass.
Matter is divided into 3 states
Solids have both a definite
volume & definite shape
Liquids have a definite
volume but no definite
shape; they can be poured
Gases do not have a
definite volume or definite
shape, but they take
the volume & shape of their
Matter consist of atoms, which are the smallest
unit of matter that can’t be broken down.
Most atoms consist of 3 particles:
Components of an Atom
around the nucleus
The simplest particle of an
element that retains all the
properties of that element
Properties of atoms
determine the structure and
properties of the matter they
Our understanding of the
structure of atoms based on
scientific models not
Consists of positive
charged protons and
Contains most of the
mass of the atom
All atoms of a given element have the same
number of protons
Number of protons called the atomic number
Number of protons balanced by an equal
number of negatively charged electrons
The number varies slightly among atoms of
the same element
Negatively charged high energy particles
with little mass
Travel at very high speeds at various
distances (energy levels) from the nucleus
Elements are pure substances which cannot be
chemically broken down into simpler kinds of
More than 100 elements have been identified,
but only about 30 are important in living things
All of the Elements are arranged on a chart
known as the Periodic Table
Periodic charts tell the atomic number, atomic
mass, & chemical symbol for every element
Four elements, Carbon – C, Hydrogen – H,
Oxygen – O, and Nitrogen – N make up almost
90% of the mass of living things
Chemical Elements cont..
Each element has an unique chemical symbol
Consists of 1-2 letters
First letter is always capitalized
The number of protons in an atom is called the atomic
number & determines which element it is.
The number of protons & neutrons is called the atomic mass
or mass #.
How do we find the #of neutrons?
Atomic mass (# of neutrons & protons)
- Atomic # (# of protons)
= # of neutrons
The number of positively charged protons is balanced
by an equal number of negatively charged electrons
Electrons at outer levels have more energy than those
in inner levels.
Each level or shell can only hold a certain # of eThe first level, nearest the nucleus can only hold two
electrons, the second and other outer levels can hold
up to eight electrons each.
A stable atom is an atom that has a full outer level
Electrons in the same energy level are
approximately the same distance from
Outer energy levels have more energy
than inner levels
Each level holds only a certain number
Substance containing two or more elements.
(glucose - sugar)
6 - carbons
12 - hydrogen
6 - oxygen
Answer the following questions about
1. How many elements are involved?
2. How many atoms are involved?
1. Elements - 3 (C, H, O)
2. Atoms - 24
The smallest unit of matter that still
retains the properties of an element.
Carbon - Atom
Protons - 6
Equals the number of protons within the
nucleus of an element.
Hydrogen (H) - 1
Equals the number of protons + neutrons.
Carbon (C) - 12
Oxygen (O) - 16
Charge of an Element
Question: protons = electrons
Question: protons electrons
charge is neutral
the charge is either negative or
Atoms of elements with different number of
carbon - 12
carbon - 13
carbon - 14
Isotopes of Carbon
orbit around the nucleus
first bonding orbital - 2 electrons
all other bonding orbitals - maximum 8 electrons
orbitals have certain energy levels
orbitals farther from the nucleus have the highest energy
Sodium and Chlorine – Electrons
Three types of bonds with different
covalent > ionic > hydrogen
two elements share one or more pairs of
single and double bonds
1. H2O (water - polar molecule)
2. CH4 (methane)
3. O2 (dioxide)
atom or molecule with an electric charge.
resulting from a gain or loss of one or
Sodium ion (Na+)
Chloride ion (Cl-)
second strongest bond
two ions with opposite charges attract
to each other.
Example: salt (NaCl)
weakest of the three bonds.
Most important and common of all bonds.
Partially positive hydrogen atom of one
molecule is attracted to the partially negative
atom of another molecule (O or N).