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.
What is beta decay?
the conversion of neutron to proton and electron which is ejected. 0/-1 Beta particle
What are the three types of beta decay?
electron capture, beta emission (b-) and positron emission (b+)
What do the three types of beta decays have in common regarding neutron and protons and the force used to do this?
They convert protons to neutrons or vice versa using the weak nuclear force.
B- decay converts what to what?
Neutron —> proton + electron
B+ positron emission particle converts what to what?
Proton —> Neutron + positron
Electron capture converts what to what?
proton + electron —–> neutron
What are the properties of beta particles?
They are high energy, low mass and greater penetration ability. They can be stopped by aluminum foil or a centimeter of plastic or glass
In electron capture where is the electron taken from in the atom?
The closest shell n=1
What is alpha decay?
When a nucleus undergoes radioactive decay that includes alpha, all three beta decays it becomes excited and comes back down to ground state with the release of energy in the form of one or more photons of electromagnetic radiation.
What are the photons that are given off in alpha decay called?
gamma photons
What are the properties of gamma photons?
they are high energy, and high frequency, have no mass and no charge. They can penetrate matter the best out of the all the radiation particles. You need a few inches of lead or about a meter of concrete to stop them from reaching you.
Which of the four types of radioactive decay changes the mass number of the parent nucleus?
Alpha only.
What is the emission spectra?
The energetic fingerprint of an atom that is produced when an element in its gaseous state is placed in glass tube and bombarded with electric current and passed through a glass prism that separates the light into its component wavelength.
What is the exponential decay equation?
N=N (initial)e^(-kt) produces a declining exponential curve where as time increases the amount of radioactive substance decreases exponentially.
What is the relationship between the decay constant and time?
k = ln2/ half life (t1/2)
They are inversely proportional to one another. As the half life of a substance increases the decay constant decreases meaning the substance decays more slowly
The energy of the photons or the particles of light emitted or absorbed can be described in what terms?
The energy of these photons can be described based on Planck’s constant which is the same for every photon and their frequency at which they are moving or wavelength at which they are traveling.
E photon = ?
E = hf= h(speed of light/wavelength)
What is h (Planck’s constant equal to)?
h = 6.63 E -34 J x seconds
What are the units of E photons?
Joules = kg x m/ s^2
what was the pre-bohr model?
Scientist then though that electrons just floated around the nucleus in non-specific pattern with arbitrary energies. If this was the case then the emission spectra for hydrogen gas would produce numerous colors instead it produces specific colors with specific energies, wavelength, and frequency implying that something was wrong with the pre-bohr model of atoms.
How did Bohr correct the Budding model of the atom?
He proposed that electrons resided in specific energy states (shells) that were separated by specific distances from the nucleus. Electrons residing further being at higher energy states and those closer at lower energy states. These electrons have QUANTIZED ENERGY!
According to Bohr’s atom which only accurately predicts the behavior of atoms or ions containing one electron how can I calculate the energy of an electron when I know what energy states (shells) it is transitioning through?
En = (-2.178E-18 J/ n^2) where N is the energy level (the shell).
What model was proposed in place of the Bohr model?
The Quantum model that maintained that electrons can exist only at discrete energy levels but that their location, path around the nucleus, and their distance differ from Bohr’s model.
What are the four quantum numbers?
n, l, ml, ms (shell, subshell, orbital orientation, and spin of the electron)
How many electrons can reside in on orbital?
two electrons
What are the three major rules for electron configuration?
- Aufbau principle
- Hund’s rule
- Pauli exclusion principle
What is Aufbau principle?
States that electrons occupy the lowest energy orbitals that are available first
What is Hund’s rule?
Electrons in the same subshell will occup the available orbitals in single manner before they pair up (pairing up takes more energy then being alone)
What is Puali exclusion principle?
States that an electron can’t have the same four quantum numbers meaning that you can’t have more than two electrons in any given orbital and two electrons in the same orbital with the same spin.
Max amount of electrons that can reside in the s orbital?
two electrons
Max amount of electrons in p orbital?
six
max amount of electrons in d orbital?
10
max amount of electrons in f orbital?
14 electrons
What are diamagnetic atoms?
Atoms with all the electrons spin paired thereby having no net magnetic field.
A diamagnetic atom will interact in what way with a magnetic field?
they will be repelled by an externally produced magnetic field.
Atoms where the electrons are not spin-paired are called?
Paramagnetic atoms (they have an odd number of electrons)
How will paragmentic atoms interact with a magnetic field?
They have a magnetic field due to their electron not being paired and therefor will be attracted into an externally produced magnetic field.
