Atomic structure Flashcards
What is a chemical element?
Substance composed of only one type of atom
What is a chemical symbol?
Letter or two letters assigned to every known type of atom
Define atom
Basis of Chem
Basis of everything in universe
Matter composed of what?
Atoms
Are there pieces of matter smaller than atoms?
Yes, neutrons, protons, electrons
Are there pieces of matter smaller than neutrons, protons, electrons?
Yes, nucleons, quarks
Relative charge of a proton?
Positive one
Relative mass of a proton?
1
Position of a proton?
Nucleus
Symbol for proton?
P, P+, N+
Relative charge of a neutron?
0
Relative mass of a neutron?
1
Position of neutron?
Nucleus
Symbol for neutron?
N, N0
Relative charge for electron
-1
Relative mass of electron?
approx 1/2000
Position of electron?
cloud
Symbol for electron?
e−, β−
Describe nucleus structure
Composed of protons and neutrons
How do you know what the charge of the nucleus is?
Charge=number of protons
How small is nucleus?
Extremely small compared to atom.
Diameter average is 10 to power -15, compared to the average atomic diameter of 10 to power of -10
How many times larger than nucleus is the atom?
100,000
Diameter average is 10 to power -15, compared to the average atomic diameter of 10 to power of -10
How much of mass of atom is nucleus?
99.9%
Due to relatively large masses of protons and neutrons compared to mass of electrons.
How dense is nucleus?
Very dense
Due to large mass and small volume
Describe electron arrangement of electrons around nucleus
Move in relatively large space, often called electron cloud, outside nucleus
As negatively charged, kept moving around nucleus by attractive electrostatic forces, between them and +vly charged nucleus.
In unchanged atom, number of protons = number of electrons.
Define atomic number
Number of protons in nucleus
Define atomic mass
Number of protons and neutrons
Shell 1 is
lowest energy level
Found closest to nucleus
As shell number increases
so does amount of energy electrons contain
What is max number of electrons in each shell?
2n squared
n= shell number
Electron configuration discrepencies
K-19 electrons
2, 8, 8, 1
Ca-20 electrons
2, 8, 8, 2
Define excited state
Sometimes electrons can move to a higher shell when they do they a called excited and have gained energy
Define ground state
Non excited electrons
How can periodic table be used to determine number of valence electrons?
1) in each vertical group all elements have same number of valence electrons
2) in a row number of valence electrons increase from one to 8 from left to right
Define electron dot diagrams?
Simple diagrams used to represent the number of valence electrons of each element
Define Octet Rule
when other elements react to form bonds they do so in such a way as to obtain an inert gas electron arrangement
Define atomic absorption spectroscopy
A technique used to measure concentration of metal irons in solution
Monitor purity of substances in industry and substances such as air, water and food.
What does atomic absorption spectroscopy do?
Detect very small quantities of metal ion ppm
How does atomic absorption spectroscopy work?
Lamp shines light of specific wavelength emitted by excited metal ion being tested
Amount of light absorbed by sample related to concentration of metal ion present
Detector analysis before and after sample is tested displays concentration reading on computer
Higher concentration of metals…?
more light will be absorbed
Define isotope
Different atoms of element which have same number of protons but different number of neutrons
Describe isotopes mass number
These atoms would have same atomic number but different mass numbers
How would you expect a molecule of hydrogen made of tritium (H-3) to react with oxygen
All isotopes of same element react similarly
Relative atomic mass equation?
Sum of (% abundance x relative atomic mass of each isotope) /100
Eg of relative atomic mass equation?
B-10: 20%
B-11: 80%
(20% x 10) + (80% x 11)/100= 10.8
Chemical and physical properties of isotopes?
Isotopes of same element have same chemical properties and different physical properties
Define relative atomic mass
Mass of atom of an element compared to the carbon 12 atom
The relative average mass of element on scale on which mass of atom of isotope C12 is exactly 12
Describe how periodic table is arranged
Increasing atomic number
Horizontal rows called periods
All elements have electrons in same principle energy level (Shell)
Verticals columns called groups
In groups all elements have same number of valence electrons
Properties of element determined by?
Number of valence electrons or group in which it is found
chlorides of group 1 elements: HCl, LiCl, NaCl
chlorides of group 2: BeCl2, MgCl2 CaCl2
How do electrons in same group react?
They have same numbers of valence electrons so react similarly.
How reactive are the noble gases
Unreactive
How reactive are the alkaline metals?
Very reactive
Define atomic radius
Size of atom, mean distance of the nucleus to valence electrons
Define valency?
Measure of the combining power of an atom with other atoms when it forms a molecule or compound eg C tends to bond with 4Cl atoms to make CCl4, where as Na only forms NaCl.
Defined ionisation energy
Amount of energy required to remove the most loosely bound electron from an atom (to form an ion) in the gaseous state
General equation for ionisation energy
M(g)+ -> M+ (g)+e
Define electronegativity
A numerical measure of electron attracting power of an atom (related but different to ionisation energy)
Metals tend to have low electronegativity and tend to loose electrons while nonmetals are high and tend to gain electrons
As move from left to right across periodic table what occurs?
Decrease in atomic radius-more protons in nucleus pull electrons closer
Increase in ionisation energy - as electrons have a stronger attraction to nucleus, more energy required to remove them
Increase in melting/boiling point of element until group 4 then decreases, as a result of type of bonding metallic to covalent network to covalent molecular.
Identify more trends in the periodic table.
Increase in electronegativity.
Decrease in metallic character.
Change in bonding of element. Metallic -> Covalent Network -> Covalent Molecular.
Decrease in electrical/thermal conductivity
Reguar pattern emerges in formulae formed between element and anther element
Trends down group in periodic table.
Decrease in the first ionisation energy
Decrease in electronegativity
Atomic radius increases
Metallic radius increases
What happens to number of valence electrons as you move down a group?
They increase by 1
Why would first ionisation energy decrease as you move down a group?
Atomic radius increases electrons further from positive nucleus
More difficult for positive nucleus to hold onto outermost electron.
Why does electronegativity decrease?
Each element has one more shell as you move downwards. Valence electrons further from nucleus. Less attraction between positive nucleus and outermost electron.
What happens to melting and boiling points as you move down a group?
It decreases. Larger atomic radius.
Less elecrostatic attraction between (metals)-decreases down a group.
Melting point/boiling point increases down a group for non-metals.
Define ions?
Atoms or molecules with a net electric charge due to the loss or gain of one or more electrons.
Define cation?
Positively charged ions
Define anions.
Negatively charged ions
Define monatomic ions.
Consisting of one atom.
Define polyatomic ions.
Consisting of many atoms.
Define ion formation.
Ions are formed when atoms lose or gain electrons in order to fulfill the octet rule and have full outer valence electron shells.
