Princeton-Atomic Structure and Periodic Trends Flashcards
What is the smallest unit of an element?
atom
Protons and neutrons collectively are called?
nucleons
In a neutral atom the number of electrons outside of the nucleus will equal what?
The protons inside the nucleus
What determines the identity of an element?
The atomic number = the number of protons
What is the mass of protons and neutron?
1.66E-27kg
The mass of protons and neutron is more than what important unit of measurement?
Atomic mass unit which is equal to 1.66E-27 kg
An electron has what mass?
9.1E-31 kg which is 5E-4 tthe mass of proton and neutron
Mass number is =?
proton + neutrons
Describe the notation used to indicated atomic number and mass number
Mass number top and atomic number is at the bottom.
What is an isotope?
An element with the same atomic number (proton number) but different neutrons. Same atomic number but different mass numbers.
What is an ion?
When an atom gains or loses an electron.
What are the four fundamental forces of nature?
The nuclear force, gravitational, electromagnetism, the weak force.
What holds a nucleus together?
the strong nuclear force which is the attraction between the proton and neutrons.
What is the strongest fundamental force?
the nuclear force (the strong force)
What ratio is important for determining the stability of an atom?
The N to Z ratio the neutron to proton ratio
What are the two forces that act on the nucleus?
The attractive force between proton and neutrons and the repulsive force between protons.
Isotopes with a proton number less than what follow the linear line of N=Z and what does that mean about their stability?
They are stable isotopes with proton number less than twenty.
As the number of protons pass 20 what trend do stable atoms follow?
The number of proton and neutrons start increasing but not at proportional rate so they deviate from the N/Z line as the ratio of neutrons to protons starts increasing in order to stabilize the repulsive force between protons.
What do atoms that are above the stability line do to fix their stability problem?
They have more neutrons than they should so most atoms that fall above will undergo beta emission and some alpha.
What is the belt of stability?
A graph of atoms plotted with the proton number on the x-axis and neutrons on the y-axis (neutrons vs protons).
In alpha decay what happens?
The equivalent of a Helium nucleus of mass 4 and proton number of 2 is ejected from the parent atom to form a more stable daughter atom.
The nucleon change by alpha decay is?
4 (nucleons = protons + neutrons)
An alpha particle has what properties?
It is high energy, low distance, and be stopped by outer layers of skin or paper.
When an atom fall below the stability belt what does it do to regain stability?
It will use the excessive protons that it can’t stabilize with neutrons to convert a proton into neutron or it will capture an electron and use it to convert a proton into a neutron.This is accomplished via electron capture and positron emission.