Download Elements and Atoms

Elements and Atoms
Elements are made of atoms. Each atom of an element is exactly the same. The atoms
that make up different elements are different. This is why different elements have different
properties.
Think of the differences between aluminum and gold. They are both metals, but they are
different. How?
The reason different elements have different properties is because the atoms that make up
different elements have different numbers of tiny particles that make them up.
The particles that make up atoms are called subatomic particles.
There are three types of subatomic particles:
1. protons (positively charged particle with big mass)
2. neutrons (neutral particle (no charge) with big mass)
3. electrons (negatively charged particle with tiny mass)
An atom has 2 areas where these subatomic particles can be found:
a) the nucleus which holds the protons and the neutrons
b) the orbits where the electrons are found.
The Periodic Table of the Elements gives information about each element. We can use
the information in the Periodic Table to figure out the number of protons, neutrons and
electrons that are in each element.
Here is how:
a.
Find the atomic number. This is the number that identifies each element. It is
found in the top, left hand corner of the square for each element in the Periodic Table.
e.g. The atomic number for oxygen is _______.
The atomic number for each element tells you how many PROTONS are in the
atom for that element.
e.g. An oxygen atom has _______ protons.
b.
In a neutral atom,
the number of protons is equal to the number of electrons.
e.g. An oxygen atom has 8 electrons.
c.
The number of neutrons must be calculated. To do this, you have to find the
element’s mass number (this is the number that is found beneath the atomic
number on the green Periodic Table, or it is found beneath the element name in the
Periodic Table in your textbook).
The mass number represents how heavy an atom would be. Since the protons
and neutrons are the particles that have a comparatively large mass, the number of
each of these particles contributes to the mass of the atom.
Number of neutrons = atomic mass number – atomic number
(same as number of protons)
Mass number = number of protons + number of neutrons
***For some of the elements on the Periodic Table, the mass number is given as a
decimal. In this case (e.g. lithium’s mass number is _______), round to the nearest whole
number (e.g. the usable mass number for lithium is _______).
Calculating Subatomic Particles for the First 20 Elements
Element
Name
Hydrogen
Helium
Lithium
Beryllium
Boron
Carbon
Nitrogen
Oxygen
Fluorine
Neon
Sodium
Magnesium
Aluminum
Silicon
Phosphorus
Sulfur
Chlorine
Argon
Potassium
Calcium
Atomic
Number
Mass
Number
Number of
Protons
Number of
Electrons
Number of
Neutrons
Drawing Diagrams of Atoms – BOHR-RUTHERFORD DIAGRAMS
Bohr-Rutherford diagrams are pictures that we draw to show where the subatomic
particles in an atom are found.
Remember: Protons and neutrons are found inside the nucleus.
Electrons are found in orbits (rings) around the nucleus.
1. The nucleus is found in the middle of the atom. To represent the nucleus, we
draw a circle. Inside that circle write P to represent protons and give the number,
and write N to represent neutrons and give the number.
e.g. the nucleus for an boron atom contains 5 protons and 6 neutrons.
5p
Nucleus
6n
2. The orbits are areas where electrons are found in an atom. There is a pattern
that must be followed to draw the electrons for any atom.
The first orbit can only hold up to 2 electrons
The second orbit can only hold up to 8 electrons
The third orbit can only hold up to 8 electrons
The fourth orbit can hold 2 electrons (only because we draw these
diagrams for the first 20 elements)
ELECTRON