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
