Pearson Chemistry Notes Ch. 4.1-4.2
4.1 Defining the Atom
Overview
cannot be seen w/ naked eye def. smallest particle of an element that retains its identity in a chemical reaction
Democritus’ Atomic Philosophy
Democritus (460 BC- 370 BC) was a Greek philosopher first suggested the existence of atoms said they were indivisible and indestructible did not explain chemical behavior did not use scientific method
John Dalton (1766-1844)
English chemist schoolteacher used experimental methods he transformed Democritus’ ideas into ideas on atoms into a scientific theory studied ratios in which elements combine in chemical reactions created “Dalton’s Atomic Theory”
Dalton’s Atomic Theory
1.i. All elements are composed of tiny indivisible particles called atoms.
1.ii. Atoms of the same element are identical. The atoms of any one element are different from those of any other element
1.iii. Atoms of different elements can physically mix together or can chemically combine in simple whole-number ratios to form compounds
1.iv. Chemical reactions occur when atoms are separated from each other, joined, or rearranged in a different combination. Atoms of one element, however, are never changed into atoms of another element as a result of a chemical reaction.
Sizing up the Atom
Atoms are very small the radii of most atoms fall within the range of 5 x 10^-11 m to 2 x 10^-10m atoms can be seen in scanning electron microscopes atoms can be moved
4.2 Structure of the Nuclear Atom
Overview
Lots of Dalton’s theory is accepted except that atoms can be divided
Atoms can be divided into three subatomic particles
Protons
Neutrons
Electrons
Subatomic Particles
Electrons
Discovered by UK physicist J.J. Thomson (1856-1940)
Are negatively charged subatomic particles.
Thomson’s Experiment passed electric current through gasses at low pressure sealed the gases in glass tubes fitted at both ends with metal disks called electrodes electrodes connected to source of electricity one electrode
Overview
cannot be seen w/ naked eye def. smallest particle of an element that retains its identity in a chemical reaction
Democritus’ Atomic Philosophy
Democritus (460 BC- 370 BC) was a Greek philosopher first suggested the existence of atoms said they were indivisible and indestructible did not explain chemical behavior did not use scientific method
John Dalton (1766-1844)
English chemist schoolteacher used experimental methods he transformed Democritus’ ideas into ideas on atoms into a scientific theory studied ratios in which elements combine in chemical reactions created “Dalton’s Atomic Theory”
Dalton’s Atomic Theory
1.i. All elements are composed of tiny indivisible particles called atoms.
1.ii. Atoms of the same element are identical. The atoms of any one element are different from those of any other element
1.iii. Atoms of different elements can physically mix together or can chemically combine in simple whole-number ratios to form compounds
1.iv. Chemical reactions occur when atoms are separated from each other, joined, or rearranged in a different combination. Atoms of one element, however, are never changed into atoms of another element as a result of a chemical reaction.
Sizing up the Atom
Atoms are very small the radii of most atoms fall within the range of 5 x 10^-11 m to 2 x 10^-10m atoms can be seen in scanning electron microscopes atoms can be moved
4.2 Structure of the Nuclear Atom
Overview
Lots of Dalton’s theory is accepted except that atoms can be divided
Atoms can be divided into three subatomic particles
Protons
Neutrons
Electrons
Subatomic Particles
Electrons
Discovered by UK physicist J.J. Thomson (1856-1940)
Are negatively charged subatomic particles.
Thomson’s Experiment passed electric current through gasses at low pressure sealed the gases in glass tubes fitted at both ends with metal disks called electrodes electrodes connected to source of electricity one electrode