Chemistry Flashcards
Atomic Models in Chronological Order
- John Dalton
- J.J. Thompson
- Ernest Rutherford
- Niels Bohr
What Expirenment Did J.J. Thompson Perform To Create His Model
Cathode Ray Tube Experiment
- Glass Tube (vacuum inside) containing negatively-charged electrode (cathode) and a positively-charged electrode (anode)
- Two oppositely-charged plates and magnets were placed around the cathode ray
- Cathode rays were attracted to the positively-charged plate, indicating that the cathode rays were negatively-charged
Difference Between John Dalton’s and J.J. Thompson’s Atomic Model
J.J. Thompson’s atomic model had electrons
What Expirenment Did Ernest Rutherford Perform To Create His Model
Gold Foil Experiment
- Alpha particles were shot at gold foil
- Most went straight through – Indicating the atom was mostly empty space
- Some were deflected – Indicating that there was a small, dense, positively-charged nucleus at the center of the atom
Difference Between J.J. Thompson’s and Ernest Rutherford’s Atomic Model
Ernest Rutherford’s atomic model had an electron orbit, most the atom was empty space, and a nucleus
What Expirenment Did Niels Bohr Perform To Create His Model
Atomic Line Spectra Experiment
- A diffraction grating can be used to separate light into its component wavelengths
- When a hot gas was used with a diffraction grating, it emitted particular lines of light (emission spectrum). When the same gas was cooled, it absorbed the same lines of light (absorption spectrum)
- Shows the electron structure of an atom is quantized and electrons can emit or absorb energy in the form of photons to move between energy levels
Difference Between Ernest Rutherford’s and Niels Bohr’s Atomic Model
Electrons orbit the nucleus in energy levels, electrons can jump between energy levels
Alkali Metals Properties
- Most reactive metals
- Not found freely in nature
- React with air and moisture
Alkaline-Earth Metals Properties
- 2 valence electrons
- Highly reactive
- Low electronegativity
Transition Metals Properties
- Good conductors of heat and electricity
- High melting points
- Unreactive
Halogens Properties
- High electronegativity
- Most reactive non-metals
- All form acids when combined with hydrogen
- Have 7 valence electrons
Noble Gases Properties
- Almost non-reactive (stable octet)
- Very low electronegativities
- Low boiling points
Subatomic Particles
Electron:
- 1- charge, no mass (0 amu)
- Found outside the nucleus
Proton:
- 1+ charge, 1amu
- Found inside the nucleus
Neutron:
- No charge, 1amu
- Found inside the nucleus
What charge does an ATOM have
An atom is electrically neutral, the number of protons and electrons are the same
How to find the number of protons in an atom
Atomic number = number of protons
How to find the number of neutrons in an atom
Mass number - number of protons (atomic number)
How to find mass number
Number of protons + number of neutrons
Isotopes
Different number of neutrons
Atomic Mass
Average mass of all isotopes
Bohr Model Diagrams
- 1’st energy level can have 2 electrons
- 2’nd and 3’rd energy can have 8 electrons
- 4’th energy level can have 18
- For the first energy level, place 2 electrons in the North position
- 2’nd to 4’th energy level, place single electrons North to West, then pair up electrons going North to West
- Bohr Model Diagrams are only used for the first 20 elements
Groups and Periods
Groups are horizontal, Periods are vertical
Stable Octet
Full valence energy level
Valence Electrons
Electrons found in the outermost occupied energy level
Cation
- Lost electrons
- More protons than electrons
- Positively charged
- Can only be formed by metals
Anion
- Gained electrons
- More electrons than protons
- Negatively charged
- Can only be formed by non-metals
Ionic Compounds
Form when an electron or electrons are transferred from a metal to a non-metal
- Electrically neutral because the ions always occur in such a ratio
Ionic Bond
The electrostatic attraction between the cations and anions in an ionic compound
Polyatomic Ionic Compounds
Ionic compounds in which one or both of the ions are polyatomic
Molecular Compounds
- Form when electrons are shared between two non-metal atoms
- Atoms are linked together in very tiny, discrete, electrically neutral particles called molecules
Covalent/Molecular Bond
- A chemical bond that involves the sharing of pairs of electrons between atoms
3 Types of Covalent Bonds
- Single Bond - Sharing of one pair of electrons
- Double Bond - Sharing of two pairs of electrons
- Triple Bond - Sharing of three pairs of electrons
7 Diatomic Elements
- Hydrogen - Chlorine
- Nitrogen - Bromine
- Oxygen - Iodine
- Fluorine
2 Polyatomic Elements
- Phosphorus
- Sulfur
Molecular Structure
The three-dimensional structure or arrangement of atoms in a molecule
Vespr Theory
A model used to predict the molecular shape from the Louis structure
- According to VESPR, electron pairs repel each other
- Lone pairs repel more than bond pairs
Electronegativity
The relative attraction of an atom for the electrons in a bond
- Increases Bottom to Top and Left to Right
Non-polar covalent bond
In a covalent bond between identical atoms, the bonding pair of electrons is shared equally
Eg. Diatomic elements
Polar covalent bond
A covalent bond between non-identical atoms with different electronegativities, where the bonding electron is shared unequally
- The unequal sharing gives the bond partial positive and partial negative poles
Molecular Polarity
The overall distribution of electronic charge in a molecule
- Opposite Molecular Polarities, eg. CO2 cancel each other out, making the overall molecule nonpolar
Properties of Ionic Compounds
- Solid at room temperature
- High melting points
- Hard and brittle
- Some are soluble (use solubility table)
- Don’t conduct electricity in solid state
- Conduct electricity in liquid form
Properties of Molecular Compounds
- Lower melting points
- State depends on size (water is an exception due to hydrogen bonding)
- Solubility depends on the polarity of the molecular compound
- Don’t conduct electricity in any state
Electrolytes
Aqueous solutions that conduct electricity
Nonelectrolyte
Aqueous solution that doesn’t conduct electrcity
Acids
Molecular compounds that contain a covalently bonded H atom
- Have a hydrogen cation
Bases
Ionic compounds that contain a OH (hydroxide) ion
- Have a hydroxide anion
pH of Ionic and Molecular compounds
Ionic and Molecular compounds both have a pH of 7
Physical Change
When a substance undergoes a change in its physical form, but the chemical composition stays the same
Chemical Change
When a substance undergoes a change in its chemical composition resulting in the formation of a new substance
Evidence of a Chemical Change
- Energy Change
- Formation of a Gas
- Formation of a Precipitate
- Color, odour, or temperature change
System
Part of the universe we focus on
Surroundings
Everything in the universe except the system
Boundary
What separates the system from its surroundings
Law of Conservation of Energy
The energy of the universe is constant; it can be neither created nor destroyed, but only transferred and transformed
Chemical potential energy
The energy stored in the chemical bonds that hold compounds together
Chemical potential energy
The energy stored in the chemical bonds that hold compounds together
Law of Conservation of Mass
Matter in a closed or isolated system is constant; it can neither be created, but only rearranged into different combinations or forms
Balancing Combustion Reactions
- Balance hydrogen so that the H2O coefficient is a even number
- Balance Carbon
- Balance Oxygen
Endothermic Reaction
Energy is absorbed from the surroundings
Exothermic Reaction
Energy is released into the surroundings
Formation (Synthesis) Reaction
Two elements combine to form a compound
- A + B => AB
Decomposition Reaction
A compound is broken down into elements
- AB => A + B
Single Replacement Reaction
A compound reacts with an element to produce a new compound and a new element
- Either a metal will replace the metal cation in a ionic compound
- A non-metal will replace the non-metal anion in a ionic compound
- Often take place in aqueous solutions
- AB + C => AC + B
Double Replacement Reaction
Two compounds react to produce two new compounds
- Often occur between two ionic compounds and take place in aqueous solutions
- The cation of the first ionic compound replaces the cation of the second ionic compound
- AB + CD => AD + CB
Precipitation Reaction (Double Replacement)
A chemical reaction in which two soluble ionic compounds form an insoluble product, a precipitate
Neutralization Reaction (Double Replacement)
Special kind of double replacement reaction that occurs when an acid or base react to produce a neutral ionic salt and water
Hydrocarbon Combustion Reaction
A hydrocarbon fuel (CₓHᵧ) is burned in the presence of oxygen to produce carbon dioxide and water vapor
- Always exothermic, so the water is released as a gas
Incomplete Combustion Reaction
Occurs when there is a poor supply of oxygen, results in carbon monoxide being released instead of carbon dioxide
Mole
6.02 x 10²³
Molar Ratios
Ratio between the amounts in moles of any two compounds involved in a balanced chemical reaction
