Chapter 1 - Atomic Structure Flashcards
Where are protons and neutrons found?
In the nucleus
Each proton has an amount of charge equal to what?
The fundamental unit of charge
e = 1.6 x 10^-19 Coulombs
Simplified as “+1e” or even “+1”
Protons have a mass of approximately what?
One atomic mass unit (amu)
What are elements defined by?
The number of protons they contain
All atoms of a given element have the same atomic number but may not contain the same mass, why is this?
Because they can have varying number of neutrons
The atomic number is what sign in chemistry?
Z
How much more does a neutron weight than a proton?
Not much at all, slightly greater in weight
Why do protons and neutrons in the nucleus make up almost all the mass of an atom?
Because the electron is of negligible weight
Mass number is given what sign in chemistry
A
What is the mass number (A)
It is the sum of protons and neutrons in the atoms nucleus
What are isotopes?
Atoms that share the same atomic number hence are the same element but have different mass numbers due to varying number of neutrons
In a written equation where is the atomic number (Z), mass number(A), and atom (X)?
The atom is after the atomic number and mass number, the atomic number being below the mass number which is on top
How does an electrons charge compare to a proton?
Their charge is equal in magnitude but in opposition of each other 1:1
The mass of an electron is approximately how much of a proton?
1/2000
Since masses of subatomic particles are so small, what does this mean for electrostatic force and gravitational force?
The electrostatic force of attraction between the unlike charges of the proton and electron is far greater than the gravitational force of attraction based on their respective masses
Why do electrons have varying levels of electrical potential?
Because they move around the nucleus at varying distances
Which electrons have lower and higher levels of energy?
Electrons closer to the nucleus are at lower levels of energy, those further have higher levels of energy
What electrons have the strongest interactions with the surrounding environment and the weakest interactions with the nucleus?
The electrons that are furthest from the nucleus, these electrons are called valence electrons
What electrons are much more likely to become involved in bonds with other atoms and why?
Valence electrons, because they have the least electrostatic pull from their own nucleus
Generally speaking What determines the reactivity of an atom?
Valence electrons
How do valence electrons play a role in increasing stability?
They can share or transfer valence electrons in bonds allowing elements to fill their highest energy levels to increase the stability
What is a positive and negative charged atom called?
Positively charged - cation
Negatively charged - anion
Atomic mass unit (amu) is equal to what?
1.66 x 10^-24g
What is the difference between Atomic weight and atomic mass
Atomic weight is the average mass of all isotopes of an element
Atomic mass refers to the mass of an individual atom of a specific isotope of that element
Is the atomic weight or atomic mass on the periodic table?
Atomic weight
What is a mole?
A mole is a unit of measurement used to quantify the amount of a substance
It represents 6.02 x 10^23 (Avogadro’s number)
What did Ernest Rutherford provide experimental evidence of in 1910?
That an atom has a dense, positively charged nucleus that accounts for only a small portion of the atoms volume
What did max Planck do in 1900?
He developed the first quantum theory, proposing that energy emitted a electromagnetic radiation from matter comes in discrete bundles called quanta, energy of quantum, given by the Planck relation
What is the Planck relation formula?
E = hf
E - energy of a photon
h - plancks constant = 6.626 x 10^-34 J•s
f - frequency of radiation
In 1913, danish physicist Neil’s Bohr used the work of Rutherford and Planck to develop his model of the electronic structure of the hydrogen atom called what?
The Bohr model
What is the equation for angular momentum when the object is moving in a circle around a fixed axis like an electron is?
L=mvr
L=angular momentum
m=mass
v=linear velocity of object
r=distance between object and the axis of rotation
What is the equation for kinetic energy?
K=1/2mv^2
K = kinetic energy
m = mass
v = velocity
Bohr placed restrictions on the possible values of the angular momentum, predicting that the possible values for the angular momentum of an electron orbiting a hydrogen nucleus could be given by what formula?
L=nh/2pie
L = angular momentum of electron
n = principal quantum number
h = Planck’s constant
What is quantization and it’s relation to chemistry?
Quantization is the process of restricting continuous values to specific discrete values meaning certain properties of particles can only have distinct quantized values
This challenges classical continuous behavior, now a fundamental principal in quantum theory, revolutionizing our understanding of the atomic and subatomic world
What does “rh” in chemistry stand for?
Rydberg constant
equal to 2.18 x 10^-18 joules
Energy of an electron has what relationship with principal quantum number (n)?
They are directly proportional, as (n) increases, the energy of the electron also increases, thus the electron is found further from the nucleus
What is the principal quantum number (n)?
It represents the energy level or shell of an electron in an atom
The orbit with the smallest, lowest energy radius is defined as what?
The ground state (n=1)
When atoms are considered in a ground state it is in the state of lowest energy, in which all electrons are in the lowest possible orbitals
If an electron was promoted to an orbit with a larger radius (higher energy) the atom was said to be in…
An excited state
An atom is in this state when at least one electron has moved to a subshell of higher than normal energy
Electrons can be excited to higher energy level (excited state) how?
By heat or other energy forms to yield excited states
How long is the lifetime of an excited state?
It is brief, electrons will return rapidly to the ground state
When an electron goes from a excited state back to a ground state what results?
Emission of discrete amounts of energy in the form of photons
What is the formula for electromagnetic energy of photons?
(If frequency is not used)
E = hc/wavelength (lambda)
E = electromagnetic energy of photons
h = plancks constant
c = speed of light in a vacuum (3.00 x 10^8 m/s)
Combination of E = hf and
f = c/lambda
MNEMONIC
as electrons go from lower energy level to a higher energy level, they get AHED, what does AHED stand for?
A - absorb light
H - higher potential
E - excited
D - distant (from the nucleus)
Energy translations do not form a continuum but rather…
Are Quantized to certain values
What is the line spectrum?
The line spectrum is composed of light at specific frequencies, each line on the emission spectrum corresponds to a specific electron transition