The periodic table Flashcards
What are diatomic molecules + halides
Group 7 elements exist as diatomic molecules (exist as pairs of atoms - share electrons)
- form single covalent bonds between non-metals
How did Mendeleev arrange the known elements into his version of the periodic table
- organised elements into vertical columns based on their properties and properties of their compounds
- arranged horizontally in order of increasing atomic weight
- left gaps in the table for undiscovered elements
- was able to predict properties of unknown elements like density and melting points
What happens when an alkali metal reacts with water/oxygen/chlorine?
water: reactions are vigorous and produce a metal hydroxide and hydrogen gas
2alkali metal +2water ->2metal hydroxide + hydrogen
oxygen: form metal oxides - form a layer of metal oxide on its surface
chlorine: form salts called metal chlorides
What is an element
What is a compound
What is a a mixture
What is a molecule
Differnece between a compound and molecule
- elements are made up of only one type of atom; pure substance
- a compound is 2 or more elements chemically bonded together
- a mixture is 2 or more elements and/or compounds not chemically bonded (can be separated through physical means)
- 2 or more atoms bonded together
The results of the alpha particle scattering experiment? +who created it/its name
created by Ernest Rutherford (nuclear model)
- most alpha particles went straight through the gold foil, without any deflection - an atom is mostly space
- some alpha particles were slightly deflected by the gold foil - nucleus of an atom is positively charged as are the alpha particles
- few particles bounced back - maass of the atom is found in the nucleus - nucleus is very dense
What is an atom overall charge/why
an atom has an overall no charge (neuteral) because number of p= number of e, so the charges cancel out
What do chemical and physical properties rely on
chemical: chemical properties rely on the electronic configure
physical: rely on mass of an element
What affects reactivity and the ability to gain or lose electrons
- distance from the nucleus
- atom radii increases
- shielding by internal electrons
- force of attraction
How did John dalton arrange the periodic table
before the discovery of subatomic particles, elements were arranged by atomic weight and not atomic number
When do displacement reactions occur
they occur when a more reactive element (usually a halogen) displaces a less reactive one
What is an isotope + properties
isotopes are atoms of the same element, with the same number of protons (and electrons) but different number of neutrons
- have the same atomic number but different mass number
- they are radioactive (due to an unstable nucleus)
What is the plum pudding model
plum pudding model - JJ Thompson
- a positively charged sphere with negative electrons distributed throughout
- no empty space
Thompson discovered electrons
Properties of alkali metals
- very reactive
- very soft, shiny, malleable, lustrous
- low density
- low melting/boiling points
- m + b points decrease going down
- react vigorously with water
- reactivity increases going down
What is the nuclear model
By Ernest Rutherford
- mostly empty space with its positive charge and most of its mass is in a dense nucleus
- electrons orbit the nucleus in shells
What are covalent bonds
sharing of electrons between non-metals
