Chapter 4

Question 1

Matter is composed of ?

Answer 1

Atoms

Question 2

Atom

Answer 2

smallest identifiable unit of an element

Question 3

Element

Answer 3

a substance that cannot be broken down into simpler substances.

Question 4

Democritus

Answer 4

if you divide matter into smaller and smaller pieces, you end up with tiny, indestructible particles.

Question 5

Dalton atomic theory: Matter is composed of atoms.

Answer 5

1. Each element is composed of tiny, indestructible particles called atoms.
2. All atoms of a given element have the same mass and other properties that distinguish them from the atoms of other elements.
3. Atoms combine in simple, whole-number ratios to form compounds.

Question 6

Atoms shape

Answer 6

spherical

Question 7

Thompson: PLUM PUDDING MODEL OF ATOM

Answer 7

An English physicist named J. J. Thomson (1856–1940) discovered a smaller and more fundamental particle called the electron.

Question 8

Thompson Discovery in Depth:

Answer 8

Electrons are negatively charged.
Electrons are much smaller and lighter than atoms.
Electrons are uniformly present in many different kinds of substances.
He proposed that atoms must contain positive charge that balances the negative charge of electrons.

Question 9

PLUM PUDDING MODEL OF ATOM

Answer 9

negatively charged electrons (yellow) were held in a sphere of positive charge (red).

Question 10

Rutherford’s Gold Foil Experiment

Answer 10

Tiny particles called alpha-particles were directed at a thin sheet of gold foil. Most of the particles passed directly through the foil. A few, however, were deflected—some of them at sharp angles.

Question 11

Nucleus

Answer 11

Most of the atom’s mass and all of its positive charge are contained in a small core

Question 12

Electrons and protons

Answer 12

The number of negatively charged electrons outside the nucleus is equal to the number of positively charged particles (protons) inside the nucleus, so that the atom is electrically neutral.

Question 13

Nucleus weight

Answer 13

The dense nucleus makes up more than 99.9% of the mass of the atom but occupies only a small fraction of its volume.

Question 14

Electrons

Answer 14

The electrons are distributed through a much larger region but don’t have much mass.

Question 15

Relative Size of the Proton and the Electron

Answer 15

If a proton had the mass of a baseball, an electron would have the mass of a rice grain.
The proton is nearly 2000 times as massive as an electron.

Question 16

Electrical Charge Is a Property of Protons and Electrons

Answer 16

• Electrical charge is a fundamental property of protons and electrons.
• Positive and negative electrical charges attract each other.
• Positive–positive and negative–negative charges repel each other.
• Positive and negative charges cancel each other so that a proton and an electron, when paired, are charge-neutral.

Question 17

The Properties of Protons, Neutrons, and Electrons

Answer 17

• Protons and neutrons have very similar masses.

- Electrons have almost negligible mass.

Question 18

Electrical Storm Provides Evidence of Charge in Matter

Answer 18

-Matter is normally charge-neutral, having equal numbers of positive and negative charges that exactly cancel.
-In an electrical storm, the charge balance of matter is disturbed.
-The quick re-balancing of charge
often occurs in dramatic ways, such as is seen in
lightning.

Question 19

How Atoms of the Elements Differ from One Another

Answer 19

Elements are defined by their numbers of protons.
It is the number of protons in the nucleus of an atom that identifies the atom as a particular element.
If an atom had a different number of protons, it would be a different element.
The number of protons in the nucleus of an atom is its atomic number and is given the symbol Z.

Question 20

Atomic number

Answer 20

The number of protons in the nucleus of an atom

Question 21

Additional elements with symbols based on their Greek or Latin names:
Pb 	
Hg 	
Fe 	
Ag 	 
Sn 	
Cu 	

Answer 21

lead 		Pb 	plumbum 
mercury 	        Hg  hydrargyrum 
iron 		Fe 	ferrum 
silver 		Ag 	argentum 
tin 			Sn 	stannum 
copper 		Cu 	cuprum

Question 22

elements were named after countries:

Answer 22

Polonium after Poland
Francium after France
Americium after the USA.

Question 23

Curium is named after:

Answer 23

Marie Curie, a chemist who helped discover radioactivity and also discovered two new elements.

Question 24

Dmitri Mendeleev

Answer 24

a Russian chemistry professor, proposed from observation that when the elements are arranged in order of increasing relative mass, certain sets of properties recur periodically.

Question 25

Metals

Answer 25

• occupy the left side of the periodic table and have similar properties.
• good conductors of heat and electricity.
• tend to lose electrons when they undergo chemical changes.

Question 26

Nonmetals

Answer 26

• occupy the upper right side of the periodic table.
• Nonmetals have more varied properties; some are solids at room temperature, while others are gases.
• As a whole, nonmetals tend to be poor conductors of heat and electricity.
• Nonmetals tend to gain electrons when they undergo chemical changes.

Question 27

Metalloids

Answer 27

semiconductors because of their intermediate electrical conductivity, which can be changed and controlled.

Question 28

Ions

Answer 28

atoms often lose or gain electrons to form charged particles called ions.

Question 29

Cations

Answer 29

Positive ions

Question 30

Anions

Answer 30

Negative ions

Question 31

Charge of an ion location:

Answer 31

• shown in the upper right corner of the symbol.

- Ion charges are usually written with the magnitude of the charge first, followed by the sign of the charge.

Question 32

Ion charge=

Answer 32

of protons—#of electrons

Question 33

example Li+ ion with 3 protons and 2 electrons=

example F- ion with 9 protons and 10 electrons=

Answer 33

3-2=1+

9-10=1-

Question 34

Isotopes

Answer 34

• Atoms with the same number of protons but different numbers of neutrons
• The number of neutrons in an isotope is the difference between the mass number and the atomic number.

Question 35

Isotopes of neon:

Answer 35

Ne-21
Ne-22
Ne-20

Question 36

The mass number (A) is :

Answer 36

the sum of the number of protons and the number of neutrons.

Question 37

Atomic Mass: The Average Mass of an Element’s Atoms

Answer 37

(%/100amu) + (%/100amu) = ___ amu

Question 38

Gallium has two naturally occurring isotopes: Ga-69, with mass 68.9256 amu and a natural abundance of 60.11%, and Ga-71, with mass 70.9247 amu and a natural abundance of 39.89%. Calculate the atomic mass of gallium.

Answer 38

60. 11%/100= 0.6011
61. 89%/100= 0.3989

(0. 601168.9256)+(0.398970.9247)=
69. 72304099
69. 72 amu

Question 39

Radioactive Isotopes

Answer 39

The isotopes that emit few energetic subatomic particles from their nuclei and change into different isotopes of different elements.