atomic structure Flashcards
Who were the first people to proprose that matter was made up of particles of elemental substances?
The greeks
What became of the Greek views of matter?
it faded
What were Democritus (460-370) ideas about matter?
- smallest paticles of matter are called atoms
- different type of atoms for every type of matter
Democritus ideas about matter were not useful in a scientific sense. why?
- no experimental evidence to support it
- did not explain the chemical behavior of atom
What did Robert Boyle do in the 1600s?
showed that gold and silver were elements and are not made up of fire, water, wind and earth
What was Dalton’s model of atom? What was it’s purpose?
- cannon ball
- proposed that atoms were tiny hard sphere
Which sub-atomic particle is the first to be discovered in the atom?
The electron in 1871
Who discovered the electrons?
J.J Thompson
Who made the plum pudding?
J.J Thompson
Which scientist 1st discovered the nucleus?
Ernest Rutherford in 1911
HOw did he discover the nucleus?
By finding alpha particles at gold foil
What did Rutherford observed?
- most alpha particles went straight through the gold foil
- only a few alpha particles wee deflected when they came close center of the atom
Why most alpha paticles passed straight through the gold foil?
b/c atoms is mainly made up of empty spaces
Why were a few alpha particles deflected?
b/c of repulsion between the alpha particles and the central core of atom
pos + pos = repulsion
What is the atom mostly made up of?
empty spaces
What are the characteristics of the nucleus?
size, density, location, charge
- much smaller than atom
- very dense, contains most of the atoms mass
- center of the atom, central core of the atom
- positive charge
What did Bohr proposed about atoms?
The atom has a very small, positively charged nucleus. Surrounded by electons orbiting the nucleus in energy levels
What was Bohr’s model of atom called?
The Planetary MOdel
WHy was Bohr’s model of the atom not accepted?
b/c experimental evidence did not support it
Wave Mechanical Model ( current model)
( 5 bullet points)
- matter consists of mass of partiles
- energy consists of waves
- evidence showed that the electron has both mass and wave like properties( dual nature)
- this dual nature of the electron has been incorporated in the most of the most curren model of atom called wave mechanical model
- in the wave mechanical model the electrons are located in orbitals
What are oribitals?
Orbitals are regions in which the electrons are most likely or probably to found. In the orbitals the electrons move with distinct energy
Describe an atom.
( 2 bullet points)
- atom is the smallest particle of an element that etains the chemical properties of that element
- contgains a small dense, positively charged nucleus srrrounded by a large space occupied by electrons
What particles are found in the nucleus?
- protons and nuetrons
- the particles found in the nucleus are collectively called nucleons
- # of nucleons = # of protons + # of neutrons
What is the overall charge of an atom?
over charge - all atoms is electrically neutral or zero
what is the formula to the overall charge of the nucleus?
nucleus charge = # of protons in nucleus
WHat is meant by the term “atomic number?”
this is the number or protons in the nucleus of an atom
atom # = # of protoms
why don’t two elements have the same atomic number?
because each element has a unique number of protons in its nucleus, no two elements have the same atomic #
What is meant by the term “ mass number”
sum of protons and neutons in the nucleus of an atom
mass number = # of protons + # of neutrons
how do we find the number of neutrons?
neutrons = mass # - atomic #
Where outside the nucleus are the electrons to be found?
- electrons ae found outside the nucleus in principle energy levels or shells
- each principal energy level can only hold a certain amount of electrons
Principal energy level (n)
n = 1 energy level
n=2 energy level
n=3 energy level
n= 4 energy level
- 2
- 8
- 18
- 32
which electron enery level has the lowest energy
1st energy level
what is meant by tht eterm electon configuration?
Electon configuration shows the distribution of electons in an atom
What are valence electrons?
Valence electrons are electrons in the outermost principal energy or shell
# of valence electrons = # of electrons in the outemost shell
What is the Lewis Dot Diagram ?
consists of a chemical symbole surounded by one to eight dots representing valence electrons
What are isotopes?
Isotopes are atoms of the same element that have the same number of protons and electrons but different number of neutrons
OR
Isotops are atoms of the same element of having the same atomic number different mass number
What is atomic mass?
- the atomic mass of an element is the average mass of all naturally occuring isotops of that element
- the atomic mass of an element is usually closest to the isotope with the highest natural abundance
What are electrons said to be in ground state?
when they occupy the lowest available energy levels
What happens when energy ( heat, light or electic) is applied to electons in the gound state?
The electrons in the ground state absorbs the energy and move up to higher energy level
What are these higher energy level called?
Excited states
Describe the electrons in excited states
electrons in the excited states have high energy and are very unstable
What will eventually happen to the electrons in the excited state?
They quickly return to the ground state by releasing energy to the form of light
WHat are the lines called shown through a spectroscope?
bright line spectrom or emission lines
Why are spectral lines known as fingerprints of elements?
Each element has its own unique bright line spectrum
What is an ion?
an ion is an electrically charged particle
What charge can an ion have?
positive and negative
Describe a positive ion
(3 bulletpoints)
- A positive ion will have more psitively charged protons than negatively charge electrons
- positive ions called cations
- positive ions are formed when an atom loses lectrons there ions how formed will have more portons than electrons
Describe negative ions
(3 bulletpoints)
- a negative ion will have more negatively charge electrons than positively charge protons
- negative ions called anions
- negative ions are formed when an atom gains electrons therefore the ion now formed will have more electrons than protons
