02/14 Atomic Structure and the Periodic Table Free Online FlashCards

What does an element’s atomic number represent?

Atomic number, Z, is the number of protons in an atom and uniquely identifies the element.

How do you calculate an atom’s number of neutrons?

The number of neutrons equals the mass number minus the atomic number: neutrons = A − Z.

What distinguishes isotopes of an element?

Isotopes are atoms of the same element with the same number of protons but different numbers of neutrons.

How is an ion’s net charge calculated?

An ion’s charge equals the number of protons minus the number of electrons: q = protons − electrons.

How is average atomic mass calculated?

Average atomic mass is the sum of each isotopic mass multiplied by its fractional abundance: average mass = Σ(fraction × isotopic mass).

What is the maximum occupancy of one orbital?

An orbital can hold no more than two electrons, and those electrons must have opposite spins.

How many electrons can the third principal level hold?

The maximum number of electrons in principal level n is 2n²; for n = 3, the maximum is 18 electrons.

What does Hund’s rule require?

Hund’s rule states that electrons occupy equal-energy orbitals singly with parallel spins before any pairing occurs.

What is the electron configuration of neutral sodium?

Sodium has the electron configuration 1s² 2s² 2p⁶ 3s¹, or the abbreviated form [Ne]3s¹.

What is typical of a group 17 element?

A main-group element in group 17 typically has seven valence electrons and often forms a 1− ion.

How does effective nuclear charge change across a period?

Across a period, effective nuclear charge generally increases because proton number rises while added electrons enter the same principal energy level.

What is the general trend in atomic radius?

Atomic radius generally decreases from left to right across a period and increases from top to bottom within a group.