SUBATOMIC PARTICLES

Question 1

- Scientists reasoned that if atoms have
negatively charged particles, they must
also have positively charged particles.
-  From his experiments with electrons, J.
J. Thomson proposed that electrons
might be embedded in a sphere of
positive charge (“plum pudding”
model of the atom).

Answer 1

THE ELECTRON

Question 2

OBJECT COULD HAVE ONE OF TWO KINDS OF ELECTRICAL CHARGES

Answer 2

Positive and negative

Question 3

A negatively charged particle.
Its existence was demonstrated by J.
J. Thomson in 1897 using a cathode
ray tube experiment.

Answer 3

THE ELECTRON

Question 4

All of an atom’s positive charge, as well as
most of its mass, is concentrated in a very
small core at the atom’s center. This center
is called the nucleus.
This led to the nuclear model of the atom.

Answer 4

RUTHERFORD’S CONCLUSION

Question 5

8 - ______
O - ______
Oxygen
15.999 - ______

Answer 5

Atomic Number
Element symbol
Atomic mass

Question 6

He designed an experiment in 1907
to test J. J. Thomson’s “plum pudding”
model of the atom.
The experiment involved bombarding a piece of gold
foil with alpha particles (positively charged helium
atoms without the electrons).

Answer 6

ERNEST RUTHERFORD

Question 7

WHY ATOMS OF
ONE ELEMENT
BEHAVE
DIFFERENTLY
FROM THOSE OF
ANOTHER
ELEMENT?

Answer 7

Because they have different charges

Question 8

negatively charged

subatomic particles

Answer 8

Electrons

Question 9

Atoms of different elements differ by the number of _____ in their nucleus.
All atoms of an element have the same number of _______.

Answer 9

PROTONS

Question 10

positively charged

subatomic particles

Answer 10

Protons

Question 11

Atoms actually are divisible. They are

composed of subatomic particles.

Answer 11

THE SUBATOMIC PARTICLES

Question 12

size of nucleus

Answer 12

Although small in size, the nucleus
accounts for about 99.9% of the mass of
an atom.

Question 13

uncharged subatomic

particles

Answer 13

Neutrons

Question 14

is the number of neutrons in the

nucleus of an element’s atom.

Answer 14

Neutron Number

Neutron = mass number – atomic number

Question 15

�The number of protons in an atom of an element is called its ______

Answer 15

atomic number

Question 16

An individual atom is electrically neutral, which means

the number of protons always equal the ________

Answer 16

number of

electrons.

Question 17

is the number of protons in the

nucleus of an element’s atom.

Answer 17

Atomic Number

Question 18

is the number of protons and

neutrons in the nucleus of an element’s atom

Answer 18

Mass Number

Mass number = proton + neutron

Question 19

When an atom loses or gains one
or more electrons, it requires a net
electrical charge and is called\_\_\_\_
Electron is the subatomic particle
that participates in chemical
change.

Answer 19

ion

Question 20

A positively charged ion forms
when atom loses electron/s
It has fewer electrons
than protons.
Examples: Li+
, Sr2+
, Al3+

Answer 20

cation

Question 21

A negatively charged ion forms when atom gains electron/s
It has more electrons
than protons.
Examples: F-
, S2-
, N3-
Number of e- = p+ + charge

Answer 21

anion)

Question 22

How many electrons do Mg2+ ions have?

Answer 22

10

Question 23

Atoms that have the same number of
protons but different number of neutrons
are called
----- are variants of a particular
element
Many elements have multiple \_\_\_\_\_. To
identify isotopes, chemist add a number
after the element’s name (mass number).
Specific \_\_\_\_\_\_ have many applications,
particularly in medical testing, imaging,
and treatment.

Answer 23

isotopes.

Question 24

How many electrons do Na+ ions have?

Answer 24

10

Question 25

The average mass of
of an element’s atoms
is called the\_\_\_\_\_\_. This is the one reflected in the
periodic table of
elements.

Answer 25

atomic mass