Practice ECAT questions with answers and explanations.
Choose an option to check your answer.
Periodic trends arise from repeating valence-shell patterns.
The periodic table organizes these regularities.
Choose an option to check your answer.
Chadwick identified the neutral nuclear particle in 1932.
Neutrons explain isotopic mass differences.
Choose an option to check your answer.
Alkali metals have one valence electron.
They commonly form +1 ions and are highly reactive.
Choose an option to check your answer.
Quantum mechanics describes electron probability distributions.
An orbital can hold up to two electrons with opposite spins.
Choose an option to check your answer.
Halogens have seven valence electrons.
They commonly form -1 ions.
Choose an option to check your answer.
The Pauli exclusion principle allows two electrons per orbital.
They must have opposite spin quantum numbers.
Choose an option to check your answer.
Noble gases have filled valence shells in their common ground states.
They are generally unreactive.
Choose an option to check your answer.
An s subshell contains one orbital.
It can hold a maximum of two electrons.
Choose an option to check your answer.
Increasing nuclear charge pulls electrons closer within the same main shell.
Effective nuclear attraction generally increases across a period.
Choose an option to check your answer.
A p subshell contains three orbitals.
It can hold a maximum of six electrons.
Choose an option to check your answer.
Additional electron shells are added down a group.
This outweighs the increased nuclear charge.
Choose an option to check your answer.
A d subshell contains five orbitals.
At two electrons per orbital, it holds ten electrons.
