Chemistry (Chapter 4)

Question 1

S1) What is an atom?

Answer 1

The smallest particle of an element that retains its unique properties.

Question 2

S1) Who is Democritus?

Answer 2

A Greek philosopher who suggest that atoms are indestructible and indivisible.

Question 3

S1) By using experimental methods, Dalton transformed Democrtius’s ideas on atoms into a scientific theory.

Answer 3

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Question 4

S1) What is Dalton’s Atomic Theory?

Answer 4

1. All elments are composed of tiny indivislbe particles called atoms.
2. Atoms of the same element are identical. The atoms of any one element are different from those of any other element.
3. Atoms of different elements can physically mix together or can be chemically combine in simple whole-number ratios to form compounds.
4. Chemical reactions occur when atoms are separated from each other, joined, or rearranged in a different combination. Atoms of one element are never changed into atoms of another element as a result of a chemical reaction.

Question 5

S2) What are the three kinds of subatomic particles?

Answer 5

Electrons, protons, and neutrons.

Question 6

S2) What are electrons?

Answer 6

Negatively charged subatomic particles. (e-)

Question 7

S2) What is a cathode Ray?

Answer 7

A stream of electrons produced at the negative electrode of a tube containing a gas at low pressure.

Question 8

S2) What are protons?

Answer 8

A positively charged subatomic particle found in the nucleus of an atom. (p+)

Question 9

S2) What are neutrons?

Answer 9

A subatomic particle with no charge and a mass of 2amu; found in the nucleus of an atom. (n0)

Question 10

S2) What is Rutherford’s Atomic Model?

Answer 10

In the nucleus atom, the protons and neutrons are located in the positively charged nucleus. The electrons are distributed around the nucleus and occupy almost all the volume of the atom.

Question 11

S3) How are elements different?

Answer 11

Elements are different because they contain different numbers of protons.

Question 12

S3) What is an atomic number?

Answer 12

The number of protons in the nucleus of an atom of an element.

Question 13

S3) What is the mass number?

Answer 13

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

Question 14

S3) What is the equation to find the number of neutrons?

Answer 14

Number of neutrons = mass number - atomic number

Question 15

S3) What are isotopes?

Answer 15

Atoms of the same element that have the same atomic number but different atomic masses due to a different number of neutrons.

Question 16

S3) Because isotopes of an element have different numbers of neutrons, they also have different mass numbers.

Answer 16

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Question 17

S3) What is atomic mass unit? (amu)

Answer 17

A unit of mass equal to one-twelfth the mas of a carbon-12 atom.

Question 18

S3) What is atomic mass?

Answer 18

The weighted average of the masses of the isotopes of an element.

Question 19

S3) What is the equation to calculate the atomic mass of an element?

Answer 19

Multiply the mass of each isotope by its natural abundance, expressed as a decimal, and then add the products.

Question 20

S1) Despite their small size, individual atoms are observable with instruments such as scanning electron microscopes.

Answer 20

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