Chapter 2: Atomic Structure Flashcards
What are elements?
Substances which cannot be broken down into simpler components by chemical reactions
What is an atom
Smallest unit of an element that can take part in chemical change
Different elements have different chemical properties but a bunch of particular atoms reacts the same as
One atom
What was John Dalton’s model after noticing hydrogen and oxygen elements always combining in fixed proportions
All matter is composed of tiny indivisible particles called atoms
Atoms cannot be created/destroyed
Atoms of the same element are alike in every way
Atoms of different elements are different
Atoms combine in small numbers to form molecules
How were atoms discovered to be destructible?
High voltage passed across 2 metal electrodes and a stream of electrons were produced (same for any element)
What is Thomson’s plum pudding model?
Atom has no net charge so
Negative electrons scattered in a postive sponge like substance
How did Rutherford test Thompson’s model
Fired alpha particles (helium nuclei 2p 2n, +charge, emitted by unstable atoms with too many protons).
They were supposed to pass through or get stuck in the sponge, instead many did pass but but some repelled and bounced back.
The large no of undeflected particles suggests that atom is mainly empty space, and large deflections occurred when + alpha collided with were repelled by a dense, central positive nucleus. The small number of deflections shows the nucleus is very small
State the relative masses and charges of the 3 subatomic particles
Proton- 1 (1.672×10^-24g) and 1+(coulomb)
Neutron- 1 and 0
Electron- 1/1840 negligible and 1-
What is mass number
Sum of protons and neutrons in an atom
Aka nucleon number
What is atomic number
Proton number defines atom to its element
Equal to electron number
How is an atom represented
Element symbol right
Mass number at the top left
Atomic number at the bottom left
What are isotopes
Atoms if the same element with same proton/electron no but different neutron nos
Why do electrons deflect more in an electric field
They’re lighter
