Exam 2 Flashcards
Mass
(g or kg) a measure of the amount of matter in an object, m=dv
Volume
(mL or cm^3) the space occupied by an object, v=m/d
Density
(g/mL or g/cm^3) amount of mass for every unit of volume, d=m/v
Metric Conversions
Kilo=1000 units Hecto= 100 units Deka= 10 units Base Unit Deci= 0.1 units Centi-= 0.01 units Milli= 0.001 units -King Henry Died By Drinking Chocolate Milk -Use dimensional analysis
Significant Figure Calculations
Purpose: to show the precision of your measurement tool.
When adding/subtracting, round the answer to the number of decimal places of the least precise measurement (ex: 20.1cm + 10cm= answer with no decimal places b/c 10 is the least precise)
When multiplying/dividing, round your answer to match the amount of significant figures in the least precise measurement (ex: 220.000g / 2mL= answer with 1 sig fig b/c 2 is the least precise measurement and has 1 sig fig)
Scientific Notation
a way to shorten very large and very small numbers to make them easier to work with.
ex: 2,500,000= 2.5 x 10^6
- move the decimal place to the space just before the last number furthest from the decimal.
Mole Conversions
One mole of anything is 6.022 x 10^23 particles
To perform Mole conversions use dimensional analysis:
ex:
How many molecules of water are in 6 mol?
(6mol / 1)(6.022x10^23 / 1mol) = 4 moles
How many moles is 8.74x10^23 atoms of platinum?
(8.74atoms / 1)(1mol / 6.022x10^23 atoms)= 1 mole
Democritus
- First person to propose that matter is composed of atoms
- atom model looked like a ball
- “Thought experiement”: if you took a material and kept dividing it in half, you should eventually reach a limit at the smallest particle, the atom
Dalton
- revived the idea that matter is composed of atoms, based on experimentation with gases
- atom model looked like a ball
- findings led him to propose the Law of Conservation of Mass
Crookes
-discovered the electron using Cathode ray experiments
Thomson
- experimented with a Cathode ray, showed that all atoms contain negative particles (electrons) along with Crookes
- put together the “plum pudding’ model, a ball with positive and negative particles scattered throughout it
- determined relative mass
Rutherford
- Gold foil experiments; shot alpha particles through the foil
- discovered the nucleus
- atom model has a nucleus in the center with electron particles around it, electron arrangement did not make sense because it portrayed an unstable atom
Bohr
- modified the Rutherford model
- model include electrons in orbitals, each orbital containing a certain number of electrons to create a stable atom
- discovered that electrons mo`ve in orbits around nucleus
Schrodinger
- made most accurate atom model today
- model features electron clouds surrounding a nucleus
Atomic Number
- equal to the amount of protons in an element
- identity of element
- 1/2 of the atomic mass
- located above each element symbol on the PT
Atomic Mass vs Mass Number
Atomic mass:
-also known as atomic weight
-the weighted average mass of an atom of an element based on the relative natural abundance of that element’s isotopes.
Mass number:
-total number of protons + neutrons in a given isotope of an atom
Relative Abundance of Isotopes
(mass of isotope x decimal form of abundance) + (mass of isotope x decimal form of abundance) + etc- add masses of each isotope together
Isotopic Notation
-At element symbol is featured big in the center
-Atomic Mass goes in the top left corner
-Atomic Number goes in the bottom left corner, technically unnecessary when given the symbol
-sometimes the charge is put in the top right corner
*Hyphenated isotope notation:
name of element- mass number of isotope
ex: Oxygen-16
Ions
- Atoms that have gained or lost electrons to become more stable
- To find an ion’s charge, add the electrons and protons together, incorporating their relative charges
Wave-particle duality of electrons and light
wave:
-Elements emit only specific colors of light when heated
-light is a form of electromagnetic radiation
-the longer the wavelength, the lower the frequency
The particle nature of light:
-quantum concept is the theory that matter can gain and lose energy only in small, specific amounts called quanta
-> concept developed by Max Planck- relates colors given off by elements to locations of electrons in discrete energy levels
3 properties of electromagnetic radiation
1) Wavelength
2) Frequency
3) Amplitude
Light Equations
As a wave: speed of light(c) = wavelength(lambda) x frequency(v)
As a particle: energy of one photon(E) = planck’s constant(h) x frequency(v)
A laser emits light of frequency 4.74 x 10^14 sec^-1. What is the wavelength of the light in nm? (1m = 1 x 10^9nm)
633 nm
A photon of light has a frequency of 1.50x10^14 Hz. Determine the wavelength and energy of the photon. Respect significant figures and write your answer in scientific notation.
wavelength: 2.00x10^-6 meters(m)
energy of the photon: 9.94x10^-20 joules(J)
Calculate the wavelength of a photon of light with a frequency of 6.5 x 10^14 Hz.
4.6 x 10^-7 m
Electromagnetic spectrum general trends
Visible Light should exist roughly in these parameters: wavelength= 300 - 800nm
frequency= something x 10^14s^-1
Energy of a photon= something x 10^-19 J/photon
Bohr’s model of the atom
- first model of the electron structure
- gives levels where an electron is most likely to be found
- incorrect today, but key in understanding the atom
- In order to determine ENERGY LEVELS (n), Bohr used energy transfer on hydrogen atoms
- Energy from an electron is released when electron falls inward, to an energy level closer to the nucleus emitting the energy (often as light)
- Energy is added to an electron when electron moves upward, to an outer energy level (absorbs energy)
- 1st shell=2 electrons
- 2nd shell=8 electrons
- 3rd shell=18 electrons
Max number of electrons at an energy level
energy level 1 - 2 electrons
energy level 2 - 8 electrons
energy level 3 - 18 electrons
energy level 4 - 32 electrons
- 1st quantum number (n)
- 2n^2 is the formula to find it
Orbital shapes, names, numbers
- 2nd quantum number (l), will always be one less than 1st quantum number (n)
- Shape of s sublevel: ball shape, l=0
- Shape of p sublevel: dumbbell shape, l=1
- Shape of d sublevel: clover shape, l=2
- Shape of f sublevel: weird shape, l=3
Electron configuration
-Shows the order in which electrons build up around the nucleus
write electron configuration for Sodium, Boron, Oxygen, and Bromine
Sodium: 1s^2 2s^2 2p^6 3s^1
Boron: 1s^2 2s^2 2p^1
Oxygen: 1s^2 2s^2 2p^4
Bromine: 1s^2 2s^2 2p^6 3s^2 3p^6 4s^2 3d^10 4p^5
How many electrons does each orbital within a shell hold?
2 electrons
Noble gas shortcut
- only show the electron configuration after the last noble gas (aka valence electrons)
- write preceding noble gas in brackets, then start at the energy level below the noble gas and continue normal
What is the electron configuration of Tellurium (using the Noble Gas shortcut)
[Kr} 5s^2 4d^10 5p^4
Valence electrons
- electrons that reside in the outermost shell surrounding an atomic nucleus
- found in the orbitals associated with an atom’s highest occupied energy level
- ex: [Kr] 5s^2 4d^10 5p^4, 5 is highest energy level-> add number of electrons tied to energy level 5-> 2 + 4 = 6 valance electrons
Orbital Notation
Practice here: https://quizizz.com/admin/quiz/5dc18e821961d7001bace424/orbital-notation-practice
What is the orbital notation for Oxygen? Determine the 4 quantum numbers (n, l, ml, ms) as well using the orbital notation.
What is the orbital notation for Iron? Determine the 4 quantum numbers as well using the orbital notation.
Pauli exclusion principle
no 2 electrons will ever have the same quantum numbers or share a room (spin state in an orbital)
-In orbital notation there will never be two side-by-side up arrows or two side-by-side down arrows in the same orbital
Aufbau principle
lower energy sublevels fill up before higher energy sublevels
-electrons will always seek the lowest energy level (unless excited by a large input of energy like heat)
Hund’s rule
electrons occupy their own orbitals before pairing up
-In orbital notation up arrows in each orbital fill up first and pair with down arrows after, if needed
Avogadro’s Number
6.022x10^23 things/mole
Speed of Light
3.00x10^8 m/s
Planck’s Constant
6.626x10^-34 Js
