Download 5 - Particles in an atom

Particles in an atom
Name:_____
Labelling an atom
Label the diagram to the left using the words
below:
Nucleus
Electron
Proton
Neutron
Substances that contain only one kind of atom are called elements. Some familiar elements are oxygen, gold, silver, and
helium. An atom is the smallest part of an element that can be broken down and still have the characteristics of that
element. All atoms are basically the same. All atoms of the same element are exactly alike; however, the atoms of a
different element will differ from other elements.
With the exception of hydrogen, all atoms have three main parts. The parts of an atom are protons, electrons,
and neutrons. A proton is positively charged and is located in the center or nucleus of the atom. Electrons are
negatively charged and are located in rings or orbits spinning around the nucleus. The number of protons and electrons
is always equal. This equality is important so that the atom is neither positively nor negatively charged. It is said to
be neutral. The third part of the atom is the neutron. Neutrons are neither positive nor negative and are located in the
center of the nucleus of an atom along with the protons. Protons and neutrons are the heavy parts of an atom. Their
combined weights are called the atomic weight of an element. Electrons are so light that we say they do not have
weight.
After reading the above, use the table below to help you understand about protons, electrons, and neutrons.
Atomic Part Weight
Charge
Where Found
Yes No Positive Negative Neutral Inside Nucleus Outside Nucleus
Proton
Electron
Neutron
Study the drawings and answer the questions at the bottom of the page.
1.
2.
3.
4.
How many protons are in atom B? __________ atom A? __________
How many neutrons are in atom B? __________ atom A? __________
How many electrons are in atom A? __________ atom B? __________
What is the atomic weight of atom B? __________ atom A? __________
HISTORY OF THE ATOM
Read the article and then answer the questions that follow.
The name “atom” was first coined by the ancient Greek scientist Democritus. Much later in 1803, an English
schoolteacher named John Dalton proposed the idea that all matter is made of atoms. Dalton thought that atoms were
small, indestructible particles. Then in 1897, electrons were discovered. This meant that atoms were made of even
smaller sub-atomic particles. In 1904, J.J. Thomson developed the “plum-pudding” model of the atom which suggested
that the atom was a sphere with electrons embedded in its surface.
Seven years later, a New Zealand physicist named Ernest Rutherford found through experimentation that the atom was
mostly empty space with a very, small but dense centre. His proposal was that the atom contained a nucleus of protons
surrounded by a large area containing electrons.
In 1923, the Japanese scientist, Nagaoka, suggested that electrons were moving in orbits around the nucleus in a way
similar to that of the planets around the sun.
Choose which meaning best suits each of these words:
9. Coined
5. Physicist
*thought of
*chemist
*minted
*scientist who studies physics
*bought
*student
2. Indestructible
*not breakable
*destroyed
*soft
6. Dense
*dumb
*heavy
*silly
3. Particle
*crumb
*small piece
*apart
7. Nucleus
*explosive
*centre
*membrane
4. Sub-atomic
*smaller than atom
*bigger than atom
*same size as atom
8.
Orbits
*space
*stars
*paths around sun
Answer these questions:
9. Who thought that atoms were small indestructible particles?
10. What model was developed to explain the existence of electrons?
11. What sub-atomic particle is thought to be in the nucleus according to the article?
12. What sub-atomic particle believed now to be in the nucleus is not mentioned in the article?