16B The Orderly Atom
How are energy levels arranged in an atom?
They are arranged by increasing energy in nested shells around the nucleus, similar to the layers of an onion.
Atoms with the same number of protons but different numbers of neutrons are known as _____________________________.
isotopes
What else can we know from a neutral atoms atomic number?
it can also indicate the number of electrons in a neutral atom of the element.
Explain what an atomic mass is and how is it represented.
mass of protons and neutrons and it is always decimal numbers
What are these different types of atoms called?
they are called isotopes
Why are valence electrons significant?
They are the electrons most responsible for the element's chemical properties.
What are the three principal subatomic particles that make up the atom?
proton, neutron, electron
Protons and neutrons have very _________________________ masses.
similar
Which subatomic particle determines an atom's chemical (element) identity?
the proton
Why are both atom mass numbers and atomic mass needed in chemistry?
used for quantitative calculations in chemical reactions and used in nuclear chemistry.
What do we call the electrons occupying the outermost energy level?
valence electrons
From a chemistry point of view the ________________ energy level of the atom is the most important.
valence or outermost
An atom's atomic mass is actually equal to/less than/greater than the sum of the masses of its subatomic particles.
It is less than since some of their mass gets converted into the binding energy that holds the nucleus together.
Explain what an atom's mass number is and what it is called.
It is the total number of protons and neutrons in an atom's nucleus. It is the actual mass of the matter in an atom measured in relative mass units called the unified atomic mass unit (u)
What is the most important use of an element's atomic number?
It is a unique element identifier and an indicator of the number of protons in an atom's nucleus.
How do atoms of the same element differ?
Atoms of a given element can differ from each other by the number of neutrons in their nuclei.
What abbreviated form is used to represent isotopes?
Isotopic notation
What is an energy level, and what particle occupies it?
It is a three dimensional region of space around an atom's nucleus where an electron has a high probability of begin found.
