CC4 - periodic table Flashcards
how did mendeleev arrange atoms into the periodic table
- based on their properties and the properties of their compounds
- realised there was a pattern if elements were put in order of atomic number, he put elements with similar properties in columns
mendeleev wrong column
- some atomic masses he had were wrong because of iscotopes
- some elements didnt fit the pattern, so he switched the order of elements to keep same properties in same columns
mendeleev predictions
- had to leave some gaps for undiscovered elements
- predicted properties of unknown by using the properties of other elements in the column
how were mendeleevs ideas supported by later evidence
when these undiscovered elements were found, the fit mendeleevs predictions
eg. predicted the chemical physical properties of germanium (he called ekasilicon)
define atomic number
indicates how many protons an element has
every atom of that element will have the same number of protons even iscotopes
Describe how the elements are arranged in the modern periodic table.
- in order of ascending atomic number
- similar properties = same column
- column = group: number of electrons in outer shell
- row = period: number of shells element has
examples of groups and periods
groups:
- group 7 - chlorine: 7 electrons in outer shell
- group 0 - neon: FULL outer shell
period:
- 3rd period - potassium: 3 electron shells
Recall the positions of metals and non-metals in the periodic table.
metals - left
non-metals - right
separated by a zigzag line from aluminium, germanium etc.
define electronic configuration
the arrangement of electrons in shells around the nucleus of the atom
how does electron configuration work
use the atomic number (or number of electrons if told)
these are the maximums:
shell 1: 2 electrons
shell 2: 8 electrons
shell 3: 8electrons
rest also have 8
