1. NJ ASK REVIEW CHEMISTRY
KMS 8th grade science

2. The atom
The smallest piece of an element that still represents that element.
The atom is made up of two main parts
Electron Cloud
Nucleus

3. The nucleus A small area in the center of an atom
Responsible for most of the atom’s mass
Contains positive charge
Contained in the nucleus:
protons
neutrons

4. PRotons Size: Charge: Location: Atomic Mass Unit (amu) =
Larger than electrons
Positive
Nucleus
1 amu

5. Neutrons Size: Charge: Location: Atomic Mass Unit (amu) =
About the same size as a proton
Neutral
Nucleus
1 amu

6. electrons Size: Charge: Location: Atomic Mass Unit (amu) =
Much smaller than protons and neutrons
Negative
Electron Cloud
1/1,840 amu

8. Atomic number The number of protons located in the atom’s nucleus.
Turn to the periodic table in your text book…can you find the atomic number in the following element boxes?
Oxygen
Potassium
Gold

9. Protons and neutrons The number of of the same element will always be
However, atoms of the same element can have
For example: every carbon atom has 6 protons, however some have 6, 7, or 8 neutrons.
protons
the same
a different number of neutrons

10. These are called…
Isotopes - atoms of the same element that have different numbers of neutrons.
Most elements have isotopes.
several

11. Mass number Average atomic mass
The sum of protons and neutrons in an atom.
Average atomic mass
The average mass of the element’s isotopes, weighted according to the abundance of each isotope.

12. The average atomic mass is and based on each isotope’s
Approximately 99% of Earth’s carbon is which is why carbon’s average atomic mass is close to 12 (12.01)
weighted
abundance on Earth
Carbon-12

13. elements Pure substance made of only one type of atom
A substance made from atoms that all have the same number of protons.

14. C Carbon element box Element Atomic Number Carbon 6 Symbol Atomic Mass
12.01

15. The arrangement of elements
Arranged by:
Arranged in order of:
Periodic-
Dmitri Mendeleev ( )
Increasing atomic mass
Describes something that occurs or repeats in regular intervals.

16. The three main regions of elements on the periodic table classify elements as
Metals, nonmetals, or metalloids

17. Columns The (up and down) columns of the periodic table are called
There are groups
Elements in the same group or family have
vertical
groups or families 18
Similar chemical and physical properties

18. Rows The horizontal rows of the periodic table are called
Elements in a period
The first element in a period is usually an active , and the last element in a period is always an inactive .
periods
are not alike in properties
solid
gas

19. Rows Atomic number (number of protons)
Atomic mass (number of protons + neutrons)
Metals are on the
Non-metals are on the
increases from left to right across a period
increases from left to right across a
period
left
right

20. Energy levels Different electrons within an atom have
An electron moves around the nucleus at a distance that corresponds to
Electrons to the nucleus have the amount of energy.
Electrons from the nucleus have the energy.
different amounts of energy
the amount of energy it has.
closest
least
furthest
most

21. Electron Energy Levels

22. Energy levels
Negatively charged are strongly attracted to charged nucleus of an atom.
These OUTERMOST electrons can easily be attracted to the nucleus of
We call these OUTERMOST electrons
electrons
positively
other atoms
valence electrons

23. Energy levels
Valence Electrons - outermost electron of an atom that participates in chemical bonding.
These attractions are what cause
chemical bonds