Unit 2 Atoms, Elements, and Compounds
Safety-Don’t do anything stupid
- 2400 has an assumed 4, but is actually infinite
- Conversions are always infinite
- Use scientific notation if you have to, but keep the required sig digs
- When calculating, the answer must have the same amount of sig digs as the number with the fewest (e.g. 90.4-10.43=80) so round
- Is mass/volume
- GRASS (given, Required, analysis, solve, statement)
PTM (Particle theory of matter)
- All matter is made out of particles
- Particles of the same substance are identical
- All particles have spaces between them
- Particles are constantly in motion
- Heat affects the speed at which particles move
- There are forces of attraction between particles
- For oxygen, insert a glowing splint into the mouth of the container of gas, if it bursts into flames, then it is oxygen
- For Hydrogen, insert a burning splint into the mouth of the container, if the splint goes out with a popping noise, then it is hydrogen
- For Carbon dioxide, bubble the gas with limewater, if it becomes cloudy, then it is carbon dioxide
- For H2O (water), if the cobalt chloride (CoCl2) changes colour from blue to pink, then it is water
Mass of Sub-Atomic Particles
In order to test the conductivity of a substance, use a conductivity apparatus.
Mixtures and Pure Substances
- Pure substances include compounds and elements
- Elements are found in the periodic table (e.g. Hydrogen-H)
- Compounds are two or more elements joined together by a bond in a fixed ratio (e.g. H2O)
- Pure substances are homogeneous (uniform throughout)
- Mixtures include homogeneous and heterogeneous
- Homogeneous mixtures are either solutions or alloys
- Alloys are metal (e.g. bronze, the nickel coin, steel)
- Solutions (e.g. sugar and water) involve the solute and the solvent
- Heterogeneous mixtures are colloids, ordinary mechanical mixtures, emulsions, or suspensions
- Suspension-when one substance sinks to the bottom cuz it’s denser-e.g. muddy water
- Emulsions-when the two liquids refuse to mix (e.g. oil and water)-when your otp doesn’t even like each other
- Colloid-when the particles are too smol that even gravity can’t break them up (too adorable) e.g. milk
- Ordinary mechanical mixture-literally everything else e.g. granite
- The Tyndall effect is how to tell colloids and solutions apart, if light is scattered by the particles, then it is a colloid
- Homogeneous mixtures appear uniform throughout whereas heterogeneous mixtures consist of visibly different substances
Properties of Matter
- Physical properties are those that can be observed (qualitative) or measured(quantitative)
- Chemical Properties describe how a substance reacts to another substance
Evidence for Chemical Changes
- Heat is produced
- A precipitate(solid that forms when 2 solutions are combined) forms
- Change in odor
- Starting material is used up (consumed)
- Heat is absorbed (gets colder)
- Change in colour
Evolution of the Atom
- Greek philosopher, father of modern atomic thought.
- Proposed that matter could NOT be divided into smaller pieces forever.
- Claimed that matter was made of small, hard particles that he called “atomos”
- Created the very first atomic theory.
- Viewed atoms as tiny, solid balls.
- Theory consisted of four statements
- Atoms are tiny, indivisible particles.
- Atoms of one element are all the same.
- Atoms of different elements are different.
- Compounds form by combining atoms.
- Discovered electrons.
- Proposed the existence of protons
- His atomic model was known as the “raisin bun model” or “plum pudding model”
- First scientist to show that the atom was made of even smaller things.
- Discovered protons and the nucleus.
- Showed that atoms have (+) particles in the center, and are mostly empty space.
- He called the center of atoms the nucleus.
- Gold Foil Experiment
- Most alpha particles went right through, some particles were deflected
- Discovered the atom is mostly empty space.
- Some particles deflected and others even bounced back
- The atom had a very dense (+) center.
- Improved on Rutherford’s model.
- Every atom has a specific number of electron shells.
- Proposed that electrons move around the nucleus in specific layers, or shells.
- Chadwick discovered neutrons.
- He called these particles neutrons.
- He discovered particles with no charge (neutrons), also found in the nucleus.
The Models of the Atoms
- Dalton’s model was just a sphere
- Thomson’s plum pudding model was negative electrons floating in a soup of charge
- Bohr Rutherford model is the current one
Bohr Rutherford and Lewis
- Bohr Rutherford diagrams have the number of protons and neutrons in writing, and the electrons circling them
- For Lewis diagrams, NEVER WRITE THE PROTON OR THE NEUTRON NUMBER, just put the valence electrons as dots or as lines
- A period is a row, it has the same number of valence shells
- A group is a column, it has the same number valence electrons
- The elements can be classified as metals, non-metals, or metalloids
Characteristics of Metals Metalloids, and Non-Metals
- Solid at room temp. (except Mercury-Hg)
- Good conductors of heat and electricity
- Solid at room temp.
- Can be shiny or dull
- Not ductile
- May conduct electricity
- Solid liquid and gas at room temp.
- Not lustrous
- Solids are brittle
- Poor or non-conductors
Properties of the groups
- Alkali Metals
- Highly reactive
- Alkaline Earth Metals
- Stronger than Alkali Metals
- Denser than Alkali Metals
- Chalogens, group 16, they exist
- Forms salts
- Noticeable colour
- Noble Gases
- Very unreactive
- Only Xenon can form compounds
Ionic and Molecular bonds
- Ionic bonds are like the friends you have because they are useful, you exchange info and get along well, they help you and you help them.
- Molecular bonds are people you really like and you share everything
- Atoms also do this, in ionic bonds, they transfer electrons and in molecular bonds they share electrons
- Ionic bonds form because you are different (metal to non-metal) so one can exchange info
- Molecular bonds are formed between people you are close to and you have to have something in common (non-metal to non-metal)
- Ionic bonds have a cation (the metal) and a anion(the other one)
- For naming, endings are mono-, di-, tri-, tetra, penta-, hexa-, hepta-,octa-,nona-,deca-
Properties of Ionic bonds
- Solid at room temp.
- Form crystal structures
- Hard and brittle
- High melting points
- Highly soluble in water
- In aqueous solution- good conductor
Properties of Covalent bonds (Molecular compounds)
- Solid, liquid, or gas at room temp.
- Forms crystal structures
- Usually soft at room temp
- Generally low melting points
- Insoluble in water
- Strong/distinctive odor