chemistry semester 1 topic test Flashcards
(67 cards)
John Dalton (1803):
Dalton introduced the modern atomic theory, suggesting that all matter is made of atoms, which are indivisible and indestructible particles. He also proposed that atoms of a given element are identical in mass and properties. He proposed the solid sphere model.
Dmitri Mendeleev (1869):
Mendeleev developed the periodic table, arranging chemical elements by atomic mass and predicting the existence and properties of undiscovered elements, demonstrating the periodic nature of the elements.
J.J. Thomson (1897):
Thomson discovered the electron through his experiments with cathode rays, proposing the “plum pudding” model of the atom, which depicted electrons embedded within a positively charged sphere.
Jean Baptiste Perrin (1909):
Perrin provided experimental evidence for the existence of atoms by studying Brownian motion, he determined the size of atoms and molecules.
Ernest Rutherford (1911):
Rutherford discovered the atomic nucleus by conducting the gold foil experiment, leading him to propose a model of the atom with a dense, positively charged nucleus surrounded by electrons.
Niels Bohr (1913):
Bohr proposed a model of the atom where electrons orbit the nucleus in discrete energy levels, explaining the stability of atoms. His model provided a simple visual aid of energy levels within an atom and how electrons were sorted within them. (positively charged nucleus with electrons around it)
Henry Moseley (1913):
Moseley determined that an element’s atomic number corresponds to the number of protons in its nucleus, leading to the reorganization of the periodic table based on atomic number rather than atomic mass.
Francis William Aston (1922):
Aston discovered isotopes using a mass spectrograph, demonstrating that elements can have atoms with the same number of protons but different masses due to varying numbers of neutrons.
James Chadwick (1932):
Chadwick discovered the neutron, a neutral particle within the atomic nucleus, which explained the existence of isotopes and led to a deeper understanding of atomic structure.
elements
the simplest substance only made up of one type of atom
what are atoms made of?
Atoms are made of protons and neutrons in the nucleus and electrons in electron shells.
Particle Relative Atomic Mass Charge
Proton 1 +1
Neutron 1 0
Electron 1/1836 -1
electron configuration
- Electrons are not evenly spread but exist in layers called shells or energy levels.
- The arrangement of electrons in these shells is often called the electron configuration.
- Each shell has a maximum number of electrons that it can hold. Electrons will fill the shells closest to the nucleus first (attracted to the nucleus).
○ 1st shell: 2
○ 2nd shell: 8
○ 3rd shell: 8 - Electron arrangement: eg (2, 8, 8)
elements on the periodic table
Elements are arranged in increasing atomic number (number of protons -> since all elements are neutral also the number of electrons).
Changes in the number of particles in the nucleus (protos or neutrons) are very rare. They only occur in nuclear processes such as radioactive decay, nuclear bombs, nuclear reactors.
relative atomic mass and isotopes
They also have a second larger number which is the relative atomic mass (number of protons + neutrons).
This number is usually not an integer and has decimal point because it is the average of all the isotopes (versions of the element with the same atomic number but different number of neutrons).
Properties of isotopes:
○ Virtually identical in their chemical reactions
○ Neutrons make little difference to chemical properties but do affect physical properties such as melting point and density.
Natural samples of elements are often a mixture of isotopes.
periodic table groups and trend
Tells you the number of valence electrons (electrons in the outer shell)
You skip the 10 columns of transition metals in the middle (1, 2 …, 3, 4, 5, 6 7, 0/8)
TRENDS DOWN A GROUP: number of valence electrons is same. Number of complete electron shells increases by one. Elements usually have similar chemical properties.
periodic table row and trend
Tells you the number of filled energy shells with at least one electron in them.
TRENDS ACROSS A PERIOD: the number of valence shell electrons increases by one. The number of complete outer shells stays the same.
group 1 and 2 (name and reactivity)
If something is in Group 1 + 2 it is alkali or alkali earth metals. They make up the S block and they are reactive metals. The reactivity of metal increases going down the group. This is because going down they toms are larger in size with more energy shells, meaning the valence electrons get further away from the nucleus so the force of attraction is weaker. The further an electron is from the positive nucleus the less energy it takes to be removed and the more reactive the element will be.
groups 3 - 12
Transition metals group 3 - 12 are less reactive and can sometimes have multiple valencies. They make up the D block.
poor metals
Poor metals a staircase that begins at aluminium with the first step having two elements aluminium and gallium. They make up the P block.
semi metals
have the properties of a metal and a non metal. A staircase from boron ending with polonium.
group 17 (reactivity and name)
Non metals: include halogen group 17 -> very reactive and dangerous. The reactivity of a non metal decreases going down the group because atoms of element get larger going down the group. The outer shell gets further away from the nucleus and is shielded by more electrons. The further the outer shell is from the positive attraction of the nucleus, the harder it is to attract another electron to complete the outer shell, decreasing reactivity.
what are the diatomic particles
There are 7 non metals that exist as diatomic particles: H, N, O, F, Cl, Br, I
group 18
Non metals also include the noble gases which are safe and don’t react with anything. All monatomic and do not form bonds with other elements. Similarly unreactive up and down the group.
valence electrons
the electrons in the outer shells
