Chapter 2.1: An Element’s Atomic Structure Determines Its Properties

Flashcards from Chapter 2.1 of Principles of Life, 3rd Edition.

Atoms

The smallest unit of a chemical element, comprised of a nucleus with protons and neutrons as well as electrons in orbitals

Element

A substance consisting of only one kind of atom that cannot be converted to another substance by ordinary chemical means

Protons

Positively charged particles in an atom that reside in the nucleus

Electrons

Negatively charged particles in an atom that reside in orbital shells around the nucleus

Neutrons

Uncharged particles in an atom that reside in the nucleus; numbers of these can vary with the isotopes of an atom

Nucleus

Where protons and neutrons are gathered in an atom

Electron shells

Where rapidly moving electrons are found, far from the nucleus, such that atoms are mostly empty space

Atomic mass

The mass of the protons plus the mass of the neutrons

Dalton (Da)

The unit of measurement of atomic mass, formerly the atomic mass unit

Atomic number

The number of protons in the nucleus; usually the top number

Periodic table

Where elements are presented in order of atomic number and organized into vertical columns; elements in the same column have the same number of electrons in the outermost shell

Valence shell

The outermost shell of an element; how many electrons reside here in the outermost s and p orbitals determine an element’s chemical properties

Isotopes

Variations of an element with different neutron counts and thus atomic mass

Bohr model

The most common model for atoms proposed by physicist Niels Bohr, where electrons orbiting the nucleus are shown in electron shells differing in distance

Atomic orbital

Where electrons actually move in each shell for a defined area of space, each with one or two electrons each, including:

• Spherical s orbitals

• Dumbbell-shaped p orbitals

• More higher energy shells with distance

Octet rule

States that an atom will lose, gain, or share electrons to achieve 8 electrons in the outermost shell

Noble gases

The elements in the last column of the periodic table with 8 electrons in the outermost shell, being unreactive to other elements

Electronegativity

An atoms’s tendency to attract electrons from another atom; smaller atoms closer to 8 electrons have higher levels of this — like the most abundant atoms H, C, N, and O

Radioactive decay

The loss of atomic particles to become different isotopes of the same element, or even other elements

• Seen with carbon-14 decaying to form nitrogen-14 for greater stability