Ch.4 Atomic Structure Flashcards
what does atomos mean?
something that cannot be cut
what are the 5 main points of John Dalton’s Atomic Theory
- matter is made of tiny, indivisible particles called atoms
- atoms of the same element are identical in shape, size and weight
- atoms of different elements are distinguished by different weights
- atoms of different elements combine in fixed, simple ratios to form compounds
- atoms cannot be destroyed or created, only re-arranged (law of conservation of energy as well)
Why do chemical reactions occur
chemical reactions occur due to the arrangement of the reacting atoms
what are isotopes?
atoms of the same element can have different weights and are called isotopes (no. of neutrons vary)
what are the 6 main points of Modern Atomic Theory
- an element is made up of atoms
- atoms are made up of protons, neutrons and electrons (are divisible)
- all atoms of an element have the same number of protons and electrons but may have a different number of neutrons (isotopes)
- atoms of different elements have a different no. of protons leading to a difference in chemical properties of said element
- atoms of different elements combine in whole numbers to form compounds
- atoms cannot be destroyed or created or changes in an ordinary chemical reaction, they are only re-arranged
what are orbits or shells
electrons revolve around the nucleus at very high speeds in paths called orbits or shells
what is an electron
sub-atomic particle that has a negative electric charge (known as a point charge)
what is a proton
positively charged subatomic particle
what is a neutron
subatomic particle that has no charge
what kind of force is present between protons and electrons
electrostatic force (like charges repel, unlike charges attract)
why do electrons not fall into the nucleus?
electrons move very fast around the nucleus
this high - speed movement prevents them from falling into the nucleus (constant motion)
(this high speed movement balances the electrostatic force of attraction between protons and electrons
what is an electronic configuration?
distribution of electrons in the shells of an atom
what is a molecule?
an electrically neutral group of two or more atoms held together by chemical bonds, formed either by gaining, loosing or sharing of electrons
atomicity
number of atoms in a molecule of an element
what are the classifications of elements based on atomicity
Monoatomic (He, Al)
Diatomic (H2, O2, N2)
Polyatomic (S8, P4)
What is a chemical formula?
an expression which states the number and type of atoms present in one molecule of the compound using symbols and subscripts
valency
the combining capacity of an atom of an element or the number of hydrogen atoms with which it combines or replaces
otherwise,
Valency is the number of electrons gained/lost/shared as an atom tried to attain the electronic configuration of the nearest noble gas
What is the octet rule?
it states that the outermost shell of an atom cannot accommodate more than 8 electrons, even if it has the capacity to hold more
what is the valence shell
outermost shell/orbit of an atom
what are valence electrons
electrons present in the valence shell
what are the different classifications based on valency of elements
Monovalent - Chlorine (Hydrogen Chloride)
Divalent - Oxygen (Water)
Trivalent - Aluminium
Tetravalent - Silicon
Pentavalent - Phosphorous
what is the valency of noble gases?
0 (no need to share, lose, or give electrons; they have completed duplets/octets)
valency of hydrogen
1
On what basis does an atom give/take electrons
whichever process takes the least energy
Ions
charged particles that are formed when an atom or group of atoms gains or loses an electrons
eg. hydrogen becomes hydrogen ion/proton when it gives its electron (aka H+)
cation
a positively charged ion
eg. Sodium (Na+ + e-), Aluminium, Calcium
Electropositivity
the ability of elements to donate electrons to form positive ions
eg. metals
how is valency for elements with 5/6/7 valence electrons calculated
8 - no. of valence electrons
anion
a negatively charged ion
eg. Chlorine (Cl + e- = Cl-), Oxygen becoming oxide ion
Electronegativity
ability of an element to receive electrons and form negative ions (anions)
what suffix is added to the name of an anion
‘ide’
eg. Chloride, Oxide, Sulphide
why do transition metals have variable valency
they can donate electrons from the penultimate (second outermost) shell
hence they show more than 1 valency
how do you differentiate between ions of elements with variable valency
suffix ‘ous’ is added to one with lower valency
suffix ‘ic’ is added to one with higher valency
eg. Fe2+ is ferrous and Fe3+ is ferric
what non metals also show variable valency
Phosphorus - 3,5 (aka Phosphorus Trichloride and Phosphorus Pentachloride)
Sulfur - 2,4,6
*these elements have empty subshells
Polyatomic Ions
group of atoms that functions as a single unit in a chemical reaction and carries a charge is called polyatomic ion
what are polyatomic ions also called
Radicals
What happens when suffix ‘ate’ is changed to ‘ite’
oxygen atom decreases
eg. Nitrate ion is NO-3 and Nitrite NO-2
what happens when prefix ‘per’ is added to ‘ate’
oxygen is increased by one
eg. Chlorate is CL3-2 and Perchlorate is CLO4-
what happens when ‘bi’ suffix is added
hydrogen atom is added
eg. Carbonate ion is CO3-2 and Bicarbonate ion is HCO3
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