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Study Guide - Chapter 11- The Atom
Be able to figure out how many protons, neutrons and electrons are needed for an
element (Atom building game)
Be able to label a diagram of an atom and be able to calculate the numbers of protons,
neutrons, electrons, mass number and whether the atom has a charge from the diagram.
Building blocks of matter:
Negative
charge
No charge
Positive
charge
Number of Protons = Atomic Number
Number of Electrons = the number of protons in a neutral atom (an atom that has no
charge)
Mass Number = Protons + Neutrons
Mass Number – Atomic Number = Number of Neutrons
Atom- the smallest particle into which an element can be divided and still be the same
substance – it is not able to be divided any further – it is composed of electrons,
protons, and neutrons.
Electron- a subatomic particle that has a negative charge – it has the least amount of
mass in the atom
Nucleus- in physical science an atom’s central region, which is made up of protons
and neutrons that are grouped together. It is dense and positively charged.
Electron cloud- a region around the nucleus of an atom where electrons are likely to
be found
Proton- a subatomic particle that has a positive charge and that is found in the
nucleus of an atom
Atomic mass unit- a unit of mass that describes the mass of an atom or molecule.
The atomic mass is the weighted average of all the naturally occurring isotopes of an
element.
Neutron- a subatomic particle that has no charge and that is found in the nucleus of
an atom
Atomic number- the number of protons in the nucleus of an atom; the atomic
number is the same for all atoms of an element and determines the identity of an
element.
Isotope- an atom that has the same number of protons (or the same atomic number)
as other atoms of the same element do but that has a different number of neutrons
(and thus a different mass number)
Electromagnetic force holds the electrons around the nucleus.
The weak force is important in radioactive atoms. In certain unstable atoms, a
neutron can change into a proton or electron.
The strong force overcomes the electromagnetic force in an atomic nucleus, holding
the nucleus together.
An atom becomes an ION when there are unequal number of protons and electrons.
Ions are atoms with a charge.
Isotopes exist because atoms of the same elements can have different numbers of
neutrons.
Mass number- the sum of the numbers of protons and neutrons in the nucleus of an
atom
Atomic mass- the mass of an atom expressed in atomic mass units
Example question concerning an iron atom.
An iron atom has 26 protons, 25 neutrons, and 25 electrons.
1. What is the atomic number of this iron atom?
Answer…..26
2. What is the mass number of this iron atom?
Answer…… 51
3. What is the name of this isotope?
Answer……Iron- 51
4. What is the charge of this ion?
Answer…….+1
Practice Questions:
1. The smallest particle into which an element can be divided and still be the same
substance is a
a. Electron
b. proton
c. atom
2. Neutrons are particles that
a. Help make up the nucleus and have no charge
b. Help make up the nucleus and are positively charged
c. Are located outside of the nucleus and are negatively charged
3. Electrons are particles that
a. Help make up the nucleus and are negatively charged
b. Help make up the nucleus and are positively charged
c. Are located outside of the nucleus and are negatively charged
4. Isotopes have different
a. Atomic numbers
b. mass numbers
c. neutrons
5. Atoms are composed of:
a. Electrons and neutrons
b. atomic mass units
b. Electrons, protons, and neutrons
6. What particles make up the nucleus?
a. Electrons and neutrons
b. neutrons
c. protons and neutrons
7. An atom becomes an ion when
a. There are equal numbers of protons and electrons
b. There are equal numbers of protons, neutrons, and electrons
c. There are an unequal number of protons and electrons
8. If a boron atom has 5 protons, 6 neutrons, and 5 electrons, it has a mass number of
a. 11
b. 10 c. 16
9. How many protons does and atom with an atomic number of 23 and a mass
number of 51 have?
a. 23
b. 51 c. 28
10. Which of the following sets of particles represents an ion?
a. 19 protons, 20 neutrons, and 19 electrons
b. 19 protons, 19 neutrons, and 18 electrons
c. 20 protons, 19 neutrons, and 20 electrons