Chapter 1: Atoms

Question 1

atomic mass

Answer 1

The average mass in amu of the atoms of a particular element based on the relative abundance of the various isotopes; it is numerically equivalent to the mass in grams of one mole of the element. Weighed according to the natural abundance of each isotope. Sometimes called atomic weight or standard atomic weight.

= Σ(fraction of isotope n) X (mass of isotope n)

Question 2

atomic mass unit (amu)

Answer 2

A unit used to express the masses of atoms and subatomic particles; defined as 1/12 the mass of a carbon atom containing 6 protons and 6 neutrons. The mass of a proton or neutron is approximately 1 amu.

Question 3

atomic number (Z)

Answer 3

The number of protons in an atom; the atomic number defines the element.

Question 4

atomic theory

Answer 4

Proposed by English chemist John Dalton.

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.
4. Atoms of one element cannot change into atoms of another element. In a chemical reaction, atoms only change the way that they are bound together with other atoms.

Question 5

atoms

Answer 5

A submicroscopic particle that constitutes the fundamental building block of ordinary matter; the smallest identifiable unit of an element.

(A water molecule is composed of 3 atoms, 1 oxygen and 2 hydrogen atoms.)

Question 6

cathode ray

Answer 6

A stream of electrons produced when a high electrical voltage is applied between two electrodes within a partially evacuated tube.

Question 7

cathode ray tube

Answer 7

A partially evacuated tube equipped with electrodes to produce cathode rays.

Question 8

cation

Answer 8

A positively charged ion.

Question 9

chemical reaction

Answer 9

A process by which one or more substances are converted to one or more different substances; see also chemical change.

Matter is neither created, nor destroyed.

Question 10

chemical symbol

Answer 10

A one- or two-letter abbreviation listed directly below its atomic number on the periodic table.

Question 11

composition

Answer 11

Classification of matter where it depends on the types of particles. (Whether there is only one type or more than one type.)

Question 12

compound

Answer 12

A substance composed of two or more elements in fixed, definite proportions.

i.e.: water

Question 13

electrical charge

Answer 13

A fundamental property of certain particles that causes them to experience a force in the presence of electrical fields.

Question 14

electron

Answer 14

A negatively charged, low-mass particle found outside the nucleus of all atoms that occupies most of the atom’s volume but contributes almost none of its mass.

Question 15

element

Answer 15

A substance that cannot be chemically broken down into simpler substances.

[Helium]

Question 16

experiments

Answer 16

A highly controlled procedure designed to generate observations that may support a hypotheses or prove it wrong. Can lead to development of scientific law.

Question 17

gas

Answer 17

the state of matter in which atoms or molecules have a great deal of space between them and are free to move relative to one another; lacking a definite shape or volume, a gas conforms to the shape and volume of its container.

Question 18

heterogenous mixture

Answer 18

A mixture in which the composition varies from one region to another.

[Wet sand: Two types of particles that separate into distinct regions.]

Question 19

hypothesis

Answer 19

A tentative interpretation or explanation of an observation.

A good hypothesis is falsifiable, which means that it makes predictions that can be confirmed or refuted by further observations.

Question 20

International System of Units

Answer 20

The standard unit system used by scientists; based on the metric system.

Question 21

ions

Answer 21

An atom or molecule with a net charge caused by the loss or gain of electrons.

Question 22

homogeneous mixture

Answer 22

A mixture with the same composition throughout.

[Tea with sugar: Two types of particles that thoroughly mix]

Question 23

isotope

Answer 23

One of two or more atoms of the same element with the same number of protons but different numbers of neutrons and consequently different masses.

Question 24

law of conservation of mass

Answer 24

The law stating that matter is neither created nor destroyed in a chemical reaction.

Question 25

law of multiple proportions

Answer 25

The law stating that when two elements (A and B) form two different compounds, the masses of element B that combine with one gram of element A can be expressed as a ratio of small whole numbers.

Question 26

law of definite proportions

Answer 26

The law stating that all samples of a given compound, regardless of their source or how they were prepared, have the same proportions of their constituent elements.

Question 27

mass number

Answer 27

(A); The sum of the number of protons and neutrons in an atom.

Question 28

liquid

Answer 28

The state of matter in which atoms or molecules pack about as closely as they do in solid matter but are free to move relative to each other, resulting in a fixed volume but not a fixed shape.

Question 29

mass spectrometry

Answer 29

An experimental method of determining the precise mass and relative abundance of isotopes in a given sample using an instrument called a mass spectrometer.

Question 30

matter

Answer 30

Anything that occupies space and has mass. It is particulate – it is composed of particles.

Question 31

metric system

Answer 31

The system of measurements used in most countries in which the meter is the unit of length, the kilogram is the unit of mass, and the second is the unit of time.

Question 32

mixture

Answer 32

A substance composed of two or more different types of atoms or molecules that can be combined in variable proportions.

Sweet tea, wet sand

Question 33

molecule

Answer 33

Two or more atoms joined chemically in a specific geometrical arrangement.

Question 34

chemistry

Answer 34

The science that seeks to understand the properties of matter by studying the structure of the particles that compose matter.

Question 35

natural abundance

Answer 35

The relative percentage of a particular isotope in a naturally occuring sample with respect to other isotopes of the same element.

Question 36

neutron

Answer 36

An electrically neutral subatomic particle found in the nucleus of an atom, with a mass almost equal to that of a proton.

Question 37

nuclear theory

Answer 37

The theory that most of the atom’s mass and all of its positive charge are contained in a small, dense nucleus.

Question 38

nucleus

Answer 38

The very small, dense core of the atom that contains most of the atom’s mass and all of its positive charge; the nucleus is composed of protons and neutrons.

Question 39

periodic table

Answer 39

A table that arranges all known elements in order of increasing atomic number; elements with similar properties generally fall into columns on the periodic table.

Question 40

proton

Answer 40

A positively charged subatomic particle found in the nucleus of an atom.

Question 41

pure substance

Answer 41

Made up of only one type of particle (one component), and its composition is invariant (it does not vary from one sample to another). Individual atoms or groups of atoms joined together.

helium, water, table sale (NaCl)

Question 42

radioactivity

Answer 42

The emission of subatomic particles or high-energy electromagnetic radiation by the unstable nuclei of certain atoms.

Question 43

scientific law

Answer 43

A brief statement or equation that summarizes past observations and predicts future ones.

It decribes how nature behaves – they are generalizations about what nature does.

Question 44

solid

Answer 44

A state of matter in which atoms or molecules are packed close to one another in fixed locations with definite volume.

Question 45

state

Answer 45

A classification of a form of matter as a solid, liquid, or gas. It depends on the relative positions of the particles and how strongly they interact with one another (relative to temperature).

Question 46

substance

Answer 46

A specific instance of matter – such as air, water, or sand.

Question 47

theory

Answer 47

A proposed explanation for observations and laws, based on well-established and tested hypothesis; a theory presents a model of the way nature works and predicts behavior beyond the observations and laws on which it was based.

Question 48

unit

Answer 48

A standard quantity used to specify measurements. To assign a number to an observation.

Question 49

anion

Answer 49

A negatively charged ion.