AP Biology Chapter 2.1 Atoms, Isotopes, Ions, and Molecules: The Building Blocks (Part 1)

Atoms

________ are the smallest unit of matter that retain all their characteristics- they consist of protons, neutrons, and electrons.

Electrons

________ will fill orbitals in a consistent order- they fill the orbitals closest to the nucleus, then continue to fill orbitals of increasing energy further from the nucleus.

Scientists

________ arbitrarily define the mass of protons as one atomic mass unit or one Dalton.

Helium

Even though ________ only has two valence electrons, its outermost shell is full, therefore, it satisfies the octet rule.

neutral atoms

In all electrically ________, the number of electrons is the same as the number of protons.

Energy levels

________ are designated by a number and the symbol "n.

Matter

________ is defined as any substance that occupies space and has mass.

Isotopes

________ are different forms of the same atom that vary in the number of neutrons.

Octet Rule

The ________ states (with the exception of the innermost shell) that atoms are more stable energetically when they have eight valence electrons.

smallest unit of matter

As mentioned before, an atom is the ________ that retains all of the chemical properties of an element.

Isotopes

________ are different forms of an element that have different numbers of neutrons, while keeping the same number of protons.

Nucleus

The _______ is the center of the atom. This region contains protons and neutrons.

Orbitals

The ________ is the outermost region of the atom. This region holds the atom's electrons in orbit around the nucleus.

positive

Protons have a ________ charge.

negative

Electrons have a _________ charge.

zero

Neutrons have a ____ charge.

Neutral atoms

The number of electrons orbiting the nucleus is equal to the number of protons inside the nucleus.

atomic number

determined by the number of protons in an atom; used to distinguish elements from each other

atomic mass

the mass of an atom of a chemical element expressed in atomic mass units; determined by adding the number of protons of a given element to the number of neutrons of that same element

periodic table

Groups elements that share certain chemical properties with other elements

Organized by atomic number

Arranged in a series of rows (periods) and columns (groups)

Bohr Model

early model of the atom developed in 1913 by Niels Bohr; depicts the atom as a central nucleus containing protons and neutrons, with the electrons in circular orbitals at specific distances from the nucleus

valence electrons

electrons of the outermost level

inert gases/noble gases

element with filled outer electron shell that is unreactive with other atoms