CHEMISTRY CH. 4 KEY CONCEPTS AND VOCABULARYGriffin Spriggs

10/21/15Period 3

4.1 Key Concepts1. How did Democritus describe atoms?

Democritus believed that atoms were indivisible and indestructible

2. How did John Dalton further Democritus’s ideas on atoms?By using experimental methods, Dalton transformed Democritus’s ideas

on atoms not a scientific theory.

3. What instruments are used to observe individual atoms?Despite they small size, individual atoms are observable with instruments

such as scanning tunneling microscopes.

4.1 VocabularyAtom: the smallest particle of an element that retains its identity in a chemical

reaction.Dalton’s Atomic Theory: the first theory to relate chemical changes to events at

the atomic level.

4.2 Key Concepts1. What are three kinds of subatomic particles?

Three kinds of subatomic particles are electrons, protons, and neutrons.

2. How can you describe the structure of the nuclear atom?In the nuclear atom, the protons and neutrons are located in the nucleus.

The electrons are distributed around the nucleus and occupy al-most all the volume of the atom.

4.2 VocabularyCathode Ray: a stream of electrons produced at the negative electrode

(cathode) of a tube containing a gas at low pressure.Electrons: a negatively charged subatomic particle.Neutrons: a subatomic particle with no charge and a mass of 1 amu: found in

the nucleus of an atom.Nucleus: the tiny, dense central portion of an atom, composed of protons and

neutrons.Protons: a positively charged subatomic particle found in the nucleus of an

atom.

4.3 Key Concepts1. What makes one element different from another?

Elements are different because they contain different numbers of protons.

2. How do you find the number of neutrons in an atom?The number of neutrons in an atom is the difference between the mass

number and atomic number.

3. How do isotopes of an element differ?Isotopes of an element differ because isotopes of an element have

different numbers of neutrons, they also have different mass num-bers.

4. How do you calculate the atomic mass of an element?To calculate the atomic mass of an element, multiply the mass of each

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

5. Why is a periodic table useful?A periodic table allows you to easily compare the properties of one

element (or a group of elements) to another element (or group of elements)

4.3 VocabularyAtomic Mass: the weighted average of the masses of the isotopes of an

element.Atomic Mass Unit (AMU): a unit of mass equal to one-twelfth the mass of a

carbon-12 atom.Atomic Number: the number of protons in the nucleus of an atom of an element.Group: a vertical column of elements in the periodic table; the constituent

elements of a group have similar chemical and physical proper-ties.

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

Mass Number: the total number of protons and neutrons in the nucleus of an atom.

Period: a horizontal row of elements in the periodic table.Periodic Table: an arrangement of elements in which the elements are

separated into groups based on a set of repeating proper-ties.