C3-C4 ATOMS, PERIODIC TABLE Flashcards
Particle
The tiny pieces that all matter is made from
Atom
The smallest independent particle everything is made of atoms
Size of atoms
About 1 x 10-10 m in diameter
Daltons model of atoms
The tiny hard spheres Can’t be broken down Can’t be created or destroyed Atoms of an element are identical Different elements have different atoms
Subatomic particles
Smaller particles that atoms are made from
Proton
Mass = 1 Charge = +1 Location = nucleus
Neutron
Mass=1
Charge = 0
Location = nucleus
Electron
Mass = 1/1835 (negligible) Charge = -1 Location= shells orbiting nucleus
Nucleus
Central part of an atom 100,000 times smaller than the overall atom
Alpha particle
Small positively charged particle made of two protons and two neutrons
Scattering
When particles bounce back or change direction
Rutherfords experiment
Fired alpha particles at gold leaf, used a phosphor-coated screen to track where they want
Rutherfolds results
Most alpha particles went through, some scattered (change direction)
Rutherfords explanation
Scattered particles hit a solid nucleus most did not hit it therefore nucleus is small
Atomic number
The bottom number on the periodic table gives the number of protons and electrons
Atomic mass
The top number on the periodic game , gives the total protons and neutrons together
Number of protons
The atomic number
Number of electrons
The atomic number
Number of neutrons
Atomic mass minus the atomic number
Number of protons and electrons
Equal, because each negative electron is attracted to a positive proton in the nucleus
Isotopes
Atoms with the same number of protons but different number of neutrons
Decribing isotopes
Mass after the name (e.g. boron-10) or superscript mass before the symbol (10B)
Nuclear fission
Large unstable atoms break into two smaller stable ones
Uses of fission
Nuclear power , nuclear weapons
Relative atomic mass
The weighted average of the masses of all the isotopes of an element
Isotopic abundance
The percentage of an element this is made of a particular isotope
Calculating
Multiply each mass by the decimal %
Add these up
Dmitri Mendeleev
Russian chemist developed the periodic table
Mendeleevs periodic table
Ordered by increasing A some elements switched according to their properties
Chemical properties
Includes reaction with acid and formula of oxide
Physical properties
Includes melting point and density
Gaps in menedeleevs periodic table
Menedeleev left gaps where no element fitted and predicted these would be filled with newly discovered elements
Eka aluminium
An element that menedeleev thought would fill a gap
He predicted its properties which matched gallium when discovered
Noble gases
Gases that do not react : he, ne, ar, kr
Moseleys experiment
Fired electrons at samples of elements and measured X-rays produced
Moseleys results
Energy of x-rays produced proportional to the positive charge of the element
Conc, from moseleys work
The atomic number must be the number of protons in the atoms
Pair reversals
Elements (like ar and k) that are not in order in increasing mass
Explaining pair reversals
It means elements should be order elements by increasing atomic number instead
Shells
Electrons orbit atoms in shells
First shell
Hold up to two electrons
Second shell
Holds up to eight electrons
Third shell
Holds up to eight electrons
Number of electrons
Given by the atomic number
Filling shells
Fills shells from the first shell out
Move up a shell when current one is full
Electron configuration
The number of electrons in each shell
E.g. Al is 2.8.3
Outer shell
The last shell with any electrons in it
Groups
Columns in the periodic table , tell you the number of electrons in the outer shell
Groups
Columns in the periodic table, tell you the number of electrons in the outer shell
Periods
Rows in the periodic table, tell you the number of electron shells
