Structure 1.2 The nuclear atom

the smallest unit of an element (having the same characteristics)

atom

Robert Boyle's Sceptical Chymist (1661)

the first one propose a modern concept of an atom being being the simplest form of an element

John Dalton's Atomic Theory (5 things)

all matter is composed of atoms, atoms cannot be created nor destroyed, atoms of the same element are similar n every way and vice versa, atoms can combine together to form molecules (fixed rations in reactions), chemical symbols for atoms

molecule

two or more atoms held together by covalent bonds

paradigm shift

a fundamental change in approach or underlying assumptions. (science evolves)

J. J. Thomson

discovered the electron by examining electricity and negative particles, "plum pudding" model with negative and positive charges in the atom

Ernest Rutherford

atoms are mostly empty space, discovered the nucleus to be very small

subatomic particles

protons, neutrons, electrons

nucleons

protons and neutrons in the nucleus

the masses of protons and neutrons

almost the same and they account for most of an atom's mass (mass number)

the mass of electrons

negligible mass

charges or subatomic particles

neutron (no charge), electron (negative charge the same strenght as the one of proton's), proton (positive charge)

Niels Bohr

discovered that electrons move around the nucleus in orbits called electron shells.

how do electrons stay in their orbits?

the oppositely charged nucleus creates an electrostatic force of attraction between negatiely charged electrons and the positivley charged nucleus

why are there neutrons in the nucleus?

to stabilize the nucleus when an atom has more than one protons in its nucleus as particles with the same charge repel each other, the neutrons prevent the nucleus from falling apart

atomic number

the number of protons (and electrons) in an atom, identifies the element

why are there equally as many protons and electrons in an atom

an atom has no overall charge

mass number (nucleon number)

the sum of the number of neutrons and protons in an atomic nucleus

which subatomic particle is responsible for chemical reactions and change?

electrons

ions

positively and negatively charged atoms

cation

a positive ions which has lost electron(s)

anion

a negative ion which has gained electron(s)

isotopes

Atoms of the same element that have different numbers of neutrons, different masses

relative atomic mass

an average mass of the most abundant isotopes of that element

do different isotopes of the same element have the same chemical characteristics?

yes as the only difference is the mass which is a physical characteristic

do different isotopes of the same elemnt have the same physical properties?

no, the mass is different and thus for example boiling and melting points vary

how can isotopes be separated

the differences in the speed of partciles at a given temperature as a greater mass slows the particles down

radioisotopes

Isotopes that have unstable nuclei and undergo radioactive decay.

what are radioisotopes used in?

medical treatments as the radioactive decay can be ued t trace to follow movement of substances in compled processes (living systems)