Science A Flashcards
(42 cards)
Dalton
Analogy: “The Billiard Ball”
- Atoms are the smallest particles of matter + are invisible
- All atoms of the same element are identical but differ from other elements
JJ Thompson
Analogy: “The Rasin Bun”
-Atoms had tiny negatively charged particles (electrons)
(Had theories based on electrons, revised the atomic theory)
Rutherford
Analogy: “nuclear”
Stated most of an atom is empty space but contains particles with a positive nucleus and electrons orbit it (gold foil)
(Discovered that atoms has a dense, positively charged core)
Bohr
Analogy: “A solar system”
-colors of light
Electrons existed in a number of energy levels (orbits nucleus)
Neutrons and protons in the middle, electrons orbit
Heisenberg + Schrodinger
Analogy: “The Cloud”
- Not possible to know the path electrons take around nucleus.
- Quantum Theory
- Mathematical
Democritus
- Ancient Greeks started the idea about atoms
- Democritus proposed that all matter was made of particles that could not be divided
- Called them Atomos (meaning invisible)
Who created the periodic table
Dmitri Mendeleev
Groups, Family, Period
Group/Family = vertical column;
-members have similar chemical properties
Period = horizontal row
Elements are classified by metals and non-metals (bold staircase)
Alkali metals, Alkali earth metals, Halogens, Noble gases
AM- Group 1 or first row on the very left (most reactive)
AEM- Group 2
Halogens - Group 17
Noble gases- Group 18 (least reactive)
Properties of metal vs non-metal
Metals- shiny, ductile, malleable, and heat conductors.
Non-metals- dull, brittle, insulators
Atomic # = Protons (Carbon is #6, so Carbon will have 6 protons)
atomic mass is Protons + Neutrons
How to find out how many electrons are in an atom or ion
In an atom, # of protons = # of electrons
In an ion, look at its charge. We know that the atomic # equals the # of protons. Oxygen has a negative charge of 2, so therefore it will have two fewer protons than electrons. (8 protons because of its Atomic# and it’ll have 10 electrons.)
Isotopes
Atoms of an element that differ in a number of neutrons and atomic mass.
Express uranium 238 in isotopic notation form
238 (atomic mass)
U
92 (atomic #)
Ions
an atom that has gained or lost electrons or has a charge, it is an ion.
If an element loses one or more electrons to become a positively charged ion, it is called a cation.
Elements that gain electrons to become ions are known as anions.
How many electron rings would magnesium have?
3 because its found in period 3
Ionic + Molecular compounds are
When 2 or more different elements chemically
combine/bond a compound is formed.
Ionic is a Cation+Anion, or metal + non-metal.
Also, make sure when writing a compound that the positively charged element goes first.
Ionic compounds
Ionic compounds are crystalline solids at SATP (standard
atmospheric temperature and pressure), have relatively
high melting points, and are good conductors of
electricity
Molecular compounds
Molecular compounds form when 2 or more nonmetallic
atoms share electrons and bond covalently. Molecular compounds may be solid, liquid, or gaseous at SATP, but tend to have relatively low melting points and are non-conductors, with the exception of acids.
Formula for water, ammonia, and hydrogen peroxide
H2O, NH3, N2O2
Buffers
Substances that can act to neutralize both acids and bases in order to minimize changes in pH
Ions have a charge and atoms don’t
hh
Process by which an acid and a base react to form water and salt (produces NaCl + H2O)
neutralization reaction
Why are acidic solutions good conductors of electricity
Because when dissolved in water they form/separate into ions, which are ideal for conducting electricity.
