Atomic Structure/Electron Configuration/Atomic Emission Spectra

Stage 1 Chemistry 2025 Term 1 Semester 1

isotope

Atoms of the same element with the same number of protons but different numbers of neutrons, resulting in different atomic masses.

ions

Atoms that have gained or lost electrons.

cations

Positively charged ions formed when an atom loses one or more electrons.

anions

Negatively charged ions formed by gaining one or more electrons.

When an atom gains an electron

an ion with a negative charge is formed (anion)

When an atom loses an electron:

an ion with a positive charge (cation)

Isotopes have the same:

chemical properties, number of electrons, and electron configurations

Isotopes have different:

physical properties, mass, density, and motion properties

atomic number

equates to the number of protons in the nucleus of an atom.

mass number

determined by the quantity of protons, and neutrons in an atom’s nucleus.

excited state

occurs when a photon absorbs energy and moves to a higher energy level/higher electron shell.

ground state

the stable state of energy, when the electron is in its lowest energy state, and has no excess energy.

photon

a particle of light energy that can either be absorbed, or emitted by an atom.

elements

only consist of one type of atom

compounds

consists of two or more elements combined together in a fixed (unchanging) ratio.

mixtures

two or more materials mixed together but not chemically combined with no fixed ratio.

Purpose for overlap between 3rd, and 4th shell:

as the size of the atoms increase, the top of the lower energy levels overlap with the bottom of the higher energy levels.

Where are the noble gases located on the periodic table?

Group A8 / far right end of the table

An element’s period number determines:

the amount of electron shells/energy levels

An element’s group number determines:

valence shell electrons (how many electrons in the outermost shell)

Why do noble gases not form molecules?

Noble gases are extremely stable, and are unable to gain/lose electrons, therefore their valence (outermost) shells are always full.

What does a filled valence shell determine?

energetically stable

Purpose of line emission spectra

each element has unique wavelengths which helps to distinguish each element in a mixture.