5.1 Atoms and Elements

Question 1

Atom

Answer 1

The smallest particles that make up all materials and can take part in chemical reactions

Question 2

Scanning Tunneling Microscope (STM)

Answer 2

A powerful microscope that can be used to see atoms, as they are too small to be seen with the naked eye.

Question 3

Indirect Evidence

Answer 3

Evidence that does not involve direct observation but provides experimental proof.

Question 4

Nucleus

Answer 4

The tight, dense bundle of protons and neutrons at the center of an atom, containing almost all of the atom’s mass.

Question 5

Electrons

Answer 5

Negatively charged particles that occupy the space surrounding the nucleus of an atom. They are attracted to the positive nucleus.

Question 5

Protons carry a —— charge, while neutrons are —–.

Answer 5

positive

neutral

Question 6

Neutrons and protons are about —- times heavier than electrons, so almost all of the atom’s mass is in the —-.

Answer 6

1800

nucleus

Question 7

Atoms are electrically —— because the number of electrons in an atom equals the number of —–.

Answer 7

neutral

protons

Question 8

Element

Answer 8

A substance composed of atoms with the same atomic number. There are 118 different elements, 26 of which are synthetic.

Question 9

Atoms are the —— that make up all materials and can take part in chemical reactions.

Answer 9

particles

Question 10

Compound

Answer 10

A substance that is made of two or more elements bonded (joined) together.

Question 11

Example: H2O - 2 Hydrogen atoms are chemically bonded to 1 Oxygen atom to form a water molecule.

Question 12

Atomic Number

Answer 12

The number of protons in the nucleus of an atom. Each atom has a unique atomic number.

Question 13

Mass Number

Answer 13

The total number of protons and neutrons in the nucleus of an atom.

Formula:
Mass Number = Number of Protons + Number of Neutrons

Question 14

Example:
Atomic Number: 11
Mass Number: 23
Element: Sodium (Na)

Question 15

Isotopes

Answer 15

Atoms that belong to the same element, with the same number of protons and the same atomic number, but have different numbers of neutrons, giving them different mass numbers.

Question 16

Isotopes have —- numbers of neutrons, resulting in different mass numbers.

Answer 16

different

Question 17

Facts: One isotope is usually much more —– (common) in nature than the others.

Answer 17

abundant

Question 18

Example: Hydrogen has three isotopes:
- Hydrogen (1H), Deuterium (2H), and Tritium (3H). All have a single proton but different numbers of neutrons.