Atomic structure and properties Flashcards
Who was James Dalton?
Father of the atom
- Revisited the theory of the atom in 1808 and created his own
- He stated that they were hard, solid, impenetrable, moveable particles
Who was Joseph Thomson?
Discovered negatively charged electrons through cathode ray experiment
-created the plum pudding model to explain his findings
Who is Rutherford?
Discovered nuclei in atoms
- fired positively charge alpha particles at gold foil
- concluded that nuclei were small and dense when some bounced back
Discovered the proton
Who was James Chadwick?
Discovered the neutron
-through bombardment of beryllium with alpha particles
Who was Neils Bohr?
Proposed a new electron configuration (Bohr model)
- electron revolve around the nucleus at fixed distances
- orbit corresponds to specific energy level
- electron cannot exist between levels
- furthest orbit is highest energy level
What is RAM?
Relative atomic mass
What is an isotope?
Two or more forms of an element that contain the same number of protons but different neutrons.
- identical chemical properties
- different mass number
How do stable isotopes occur?
-balance between attractive and repulsive forces in the nucleus
How do isotopes become unstable?
When the forces in the nucleus are unbalanced
Define isotopic composition
Shows isotopes which are present in a sample to what %/
e.g.( mass(%) + mass(%) )/100
What is mass spectrometry?
Used to qualitatively and quantitively identify elements present in a compound or mixture
What is the process of mass spectrometry?
Vaporising-separation of substance to gas state
Ionising-gas phase atoms then ionised (now have a charge)
Accelerating-pass through electric field to accelerate
Deflecting-charge deflected in magnetic field (more mass=less deflection)
Detecting-ions are analysed after being collected and abundance is measured
How is an atom held together?
Electrostatic attraction between the opposing protons and electrons
How is the nucleus held together?
Strong nuclear forces that occur regardless of change as well as electrostatic repulsion
What is atomic number?
Number of protons in the nucleus
What is mass number?
Number of protons and neutrons in the nucleus
What is an ion?
A positively/negatively charged atom or group of atoms
What is electrostatic attraction? and it’s periodic table trend?
Attraction between positive and negative charges in the atom that form chemical bonds
- increase charge difference=higher attraction
- inversely proportional to the distance between charges
- proportional to charge magnitude
What is core charge? and it’s trend
Effective nuclear charge felt by an outer electron and proton in the nucleus
- equal to nuclear charge - total number of electrons in inner shell
- remains constant down a group
- increase across a period
Explain the core charge trend
Increase across period:
- shielding stays same
- protons and electrons increase
- attraction increases
Same down group:
- ratio of electrons and protons being increased is proportional
- so no increase in attraction
What is atomic radius? and it’s trend?
Measured as the distance from nucleus to the outer shell
- decrease across period
- increase down a group
Explain the atomic radius trends
Decrease across a period:
- protons and electrons increase
- attraction therefore increases to the electrons
- shielding stays the same
- radius will decrease
Increase down a group:
- shell number increases
- decrease in attraction to valence electrons
What is first ionisation energy? trend?
The energy required to remove the first valence electron from an atom of an element in it’s “gaseous state”
- increase across a period
- decrease down a group
Explain the ionisation energy trend
Increase across a period:
- core charge increases (due to number of p and e increasing while shielding is same)
- electrons becomes harder to remove
Decrease down a group:
- atomic radius increases
- weaker attraction between nucleus and electrons
- electrons easier to lose
What is successive ionisation energy?
Energy required to remove remaining electrons after the first valence electron is removed from an element in it’s gaseous state
decrease in atomic radius=increase energy required to ionise valence electrons
What is shielding?
The decrease in attraction between an electron and the nucleus in any atom with more than one electron shell
-decreases electrostatic attraction
What is electronegativity?
The ability of an atom to attract a pair of electrons in a covalent bond
Explain electronegativity trends
Increases across a period:
- core charge increases
- radius decreases
- shielding stays the same while protons increase
- attraction therefore increases between valence electrons and the nucleus
What is metallic character?
Describes how closely an element exhibits properties associated with metals
-readily loses an electron to form a cation
-bottom left of the periodic table
small ionisation energy=greater metallic character
