1&2) Key Concepts in Chemistry A Flashcards
how has the Dalton method changed over time?
-discovery of subatomic particles…. electrons
what is the structure of an atom?
- nucleus with protons+neutrons
- electrons surrounding in electron shells
what is the relative mass and relative charge of a proton?
- RC- +1(positive)
- RM- 1
what is the relative mass and relative charge of a neutron?
- RC-0(no charge)
- RM- 1
what is the relative mass and relative charge electron?
- RC- -1(negative)
- RM- 1/1835 (negligible
why do atoms contain equal numbers of electrons and protons?
- no overall charge
- charges cancel out
how big is the atoms nucleus compared to the whole thing?
-nucleus can be 100,000 smaller diameter
where is most of the mass in an atom?
-in the nucleus
what is the mass number of an atom? where is it found?
- protons+neutrons
- top number
what is the atomic number?where is it found?
- protons only
- bottom number
what is an isotope?
- same element
- same atomic number
- different mass number
if you have the mass number and atomic number how do you work out how many protons, neutrons and electrons there are?
atomic number= -number of protons
-same number of electrons
mass number= neutrons+protons
what are relative atomic masses compared to?
-carbon-12
how does the existence of isotope result in not having whole number relative atomic masses?
- takes into account all of the isotopes
- amount of each isotope
how do you work out the relative atomic mass?
and what is the symbol for RAM?
number of atoms
-Ar
EXAMPLE
if the abundances of the two isotopes of chlorine are 75% of 35. and 25% of 37
CL CL.
17 17
how do you work out the relative atomic mass?
100
how did Mendeleev arrange the elements known at the time?
- order of RAM (but he wasn’t always right)
- left gaps
- swapped them to suit their chemical properties and their compounds
how did Mendeleev use the table to predict elements not discovered?
-properties of near by elements
how are elements arranged in the periodic table today?
- elements in rows/periods are increasing atomic number order
- smilar properties in the same colour/group
- non metals ont he right
what are the connections with the electric configuration and the periodic table?
- number of shells is equal to period number
- number of electrons in the outer shall is the same to the group number
how are cations formed?
- metal atoms
- loose electrons
- form positive ions
how are anions formed?
- non metals
- gain electrons
- form negative ions
what is an ion?
-an atom or group of atoms with a positive or negative charge
in group 1 how many outer electrons are there? how many electrons lost or gains? charge on ion? example.
- 1 electron in the outside shell
- 1 electron lost
- 1+ charge
- Li+
in group 2 how many outer electrons are there? how many electrons lost or gains? charge on ion? example.
- 2 electrons in the outside shell
- 2 electrons lost
- 2+ charge
- Ca^2+
in group 6 how many outer electrons are there? how many electrons lost or gains? charge on ion? example.
- 6 electrons in the outer shell
- 2 electron gained
- 2- charge
- S^2-
in group 7 how many outer electrons are there? how many electrons lost or gains? charge on ion? example.
- 7 electrons in the outer shell
- 1 electron gained
- 1- charge
- F-
what does it means when a compound ends in -ate or -ide?
-ion contains oxygen
Examples of ionic compounds coming together:
sodium sulfide contains the ions Na+ and S2-
-Na˘2S
what is the structure of an ionic compound?
- strong electrostatic forces
- arranged in lattice structure
