Atoms, Ions, & Isotopes
Most of an atom’s mass is found in which part of the atom?
The nucleus (protons and neutrons).
Who first proposed that matter is made of tiny, indivisible particles called atoms?
Democritus
According to the Aufbau principle, electrons fill which orbitals first?
Lowest energy orbitals.
What is the region where there is a high probability of finding an electron called?
An orbital
Which number is unique to every element and equals the number of protons?
Atomic number
What did Bohr state about atomic structure?
Electrons move in circular orbits at fixed distances from the nucleus.
What does Hund’s rule state about how electrons fill orbitals?
They fill empty orbitals before pairing up.
What is the shape of an s orbital?
Sphere
What is the difference between an ion and an isotope?
ions are a loss or gain of electrons, while an isotope is an element witha different number of neutrons
What was Thomson’s model of the atom called, and what did it describe?
The “Plum Pudding Model,” where electrons are spread throughout a positive sphere.
What does the Pauli Exclusion Principle state?
Electrons in the same orbital must have opposite spins.
How many orbitals are in the d sublevel?
5 orbitals
What happens when an atom loses electrons?
It becomes a positively charged ion (cation).
Which model is the current one used today that estimates where electrons are most likely found?
Quantum Mechanical Model
Write the standard electron configuration for sodium (Na).
1s² 2s² 2p⁶ 3s¹
What is the maximum number of electrons that can occupy a p sublevel?
6 electrons
An element has an atomic number of 76. How many protons and electrons are in a neutral atom?
76 protons and 76 electrons.
How did Rutherford’s gold foil experiment change the existing model of the atom proposed by Thomson?
Rutherford discovered that atoms have a small, dense, positively charged nucleus where most of the mass is concentrated, disproving Thomson’s “Plum Pudding” idea of evenly spread positive charge.
Write the noble gas configuration for vanadium (V).
[Ar] 4s² 3d³
What is the next sublevel after 1s, 2s, 2p, 3s, 3p?
4s