Study Guide

1
Chapter 4.2
2
Study Guide
Source Campbell, N.A., Williamson, B., and
Heyden, R.J. (2004) Biology Exploring Life.
Upper Saddle River, New Jersey Pearson
Education, Inc., Chapter 4.
3
Q1atom
4
A1

• An atom is the smallest particle of an element.

5
Q2proton
6
A2

• A proton is a subatomic particle with a single
  unit of positive electrical charge ().

7
Q3electron
8
A3

• An electron is a subatomic particle with a
  single unit of negative electrical charge (-).

9
Q4neutron
10
A4

• A neutron is a subatomic particle that is
  electrically neutral, meaning it has no
  electrical charge.

11
Q5nucleus
12
A5

• The nucleus in an atom is the central core that
  contains protons and neutrons.

13
Q6Atomic number
14
A6

• All atoms of a particular element have the same
  number of protons, known as the atomic number.

15
Q7Isotope
16
A7

• An isotope is a different form of an element ,
  which differs in its number of neutrons.

17
Q8Radioactive isotope
18
A8

• In a radioactive isotope the nucleus is unstable
  and breaks down over time, giving off matter and
  energy.

19
Q9Energy levels
20
A9Energy levels

• Electrons are not located in the nucleus of an
  atom, they belong to certain energy levels.
• The lowest energy level, nearest the nucleus, can
  hold 2 electrons.
• The second energy level can hold 8 electrons

21
Q10Describe three kinds of subatomic particles
and tell how they are arranged in an atom.
22
A10 Describe three kinds of subatomic particles
and tell how they are arranged in an atom.

• Protons are positively charged particles.
• Electrons are negatively charged particles.
• Neutrons are particles with no charge.
• Protons and neutrons make up the nucleus of an
  atom, while electrons move constantly outside the
  nucleus.

23
Q11What is an isotope? Explain the significance
of the number of electrons in an atoms highest
energy level.
24
A11What is an isotope? Explain the significance
of the number of electrons in an atoms highest
energy level.

• An isotope is one of several forms of an element,
  each containing the same number of protons in
  their atoms but a different number of neutrons.
• Radioactive isotopes can be tracked, allowing
  scientists to find out how elements are used in
  organisms.

25
Q12Describe the significance of the number of
electrons in an atoms highest energy level.
26
A12 Describe the significance of the number of
electrons in an atoms highest energy level.

• The number of electrons in an atoms highest
  energy level determines how the atom reacts.
• Atoms will react when the highest energy level is
  partly filled.

27
Q13Explain the significance of an elements
atomic number.
28
A13Explain the significance of an elements
atomic number.

• An elements atomic number, or number of protons,
  is unique. It identifies the element.

29
Q14Describe the three types of small particles
within an atom and explain how they are arranged.
30
A14

• Protons have a single unit of positive electrical
  charge ().
• Electrons have a single unit of negative
  electrical charge (-).
• Neutrons have no electrical charge.
• Protons and neutrons are tightly packed in the
  center of the atom forming the nucleus. Electrons
  move around the outside of the nucleus at great
  speed.

31
Q15How does an isotope and a radioactive isotope
differ?
32
A15

• Isotopes are a different form of element with a
  different number of neutrons.
• The nucleus of a radioactive isotope breaks down
  , regular isotopes dont.

33
Q16Which atom is likely to be more chemically
reactive, an atom with a partly filled energy
level or an atom with all energy levels
completely filled?

34
A16

• An atom with a partly filled energy level will be
  more chemically reactive.
• It is more reactive because it wants to have its
  energy levels filled.