LECTURE
THE ATOMIC NATURE OF MATTER
INTRODUCTORY QUESTIONS?
1. What is an atom?
2. What is an element?
3. What is a molecule?
4. How many atoms in a water molecule?
5. How many elements in a water molecule?
6. What makes hydrogen the lightest element in the universe?
7. What percentage of the universe is hydrogen?
8. How old are the atoms that make up your body?
9. What is meant by “atoms are recycled”?
10.How many atoms do you inhale with each breath?
ELEMENTS
-Atoms are the smallest particles of an element that can be identified with
that element.
-Atoms are composed of protons and neutrons in a nucleus surrounded
by electrons
-Elements are substances made up of only one kind of atom.
-To date there are 115 known elements.
-About 90 elements occur naturally.
-More than 99% of the material on Earth is formed from about a dozen
elements.
-Hydrogen consists of one proton and, sometimes, one electron so it is the
lightest element in the universe.
THE AGE OF ATOMS
-The atoms which make up your body are as old as the universe. You are
literally made of stardust.
-The atoms which make up your body are constantly being recycled. When
you breathe in, the oxygen atoms which were once a part of someone
else become part of your body. You are really just borrowing the atoms
which make YOU from the universe.
THE SIZE OF ATOMS
-About 1023 atoms make up a thimbleful of water.
-You inhale billions of trillions of atoms with every breath
-Atoms are perpetually in motion.(BROWNIAN MOVEMENT is the
perpetual jiggling of particles just big enough to be seen due to the
movement of atoms and molecules)
-It takes about six years for one exhaled breath to become evenly mixed
with the environment.
MOLECULES AND COMPOUNDS
-Two or more atoms are called a molecule. H2O has two hydrogen atoms
and one oxygen atom. 2H2O is two water molecules.
-A compound is a substance made of atoms of different elements
combined in fixed proportions.
-Compounds have different properties from the elements they are made of.
THE STRUCTURE OF THE ATOM
-An atom is mostly empty space.
-The nucleus was discovered by Ernest Rutherford.
-The nucleons of an atom’s nucleus are held together by the
strong nuclear force.
-The building blocks of the nucleus are called nucleons, they are
the protons(+) and the neutrons.
-All protons are identical no matter what atom they are part of.
-All neutrons are identical no matter what atom they are part of.
-Atoms of each element are identified by the number of PROTONS.
-The number of neutrons in an atom can vary. These different forms of
the same element are called isotopes.
-For a neutral atom, the number of electrons orbiting the nucleus will
equal the number of protons; if these numbers don’t match, the atom has
a charge and it is called an ion.
THE PERIODIC TABLE
-The periodic table is a method of grouping elements based on specific
characteristics.
-Elements in the same column(group) have similar chemical properties and
interact with other elements in a similar way because they have the same
number of electrons in their outer shells.
-Elements increase in the number of protons as the periodic table is read
from left to right.
THE PHASES OF MATTER
-Matter exists in FOUR phases; solids, liquids, gases and plasma
-Matter can change from one phase to another.