Periodic cairt

The periodic cairt o the chemical elements is a list o kent atoms (chemical elements). In the cairt the elements are placed in the order o thair atomic nummers stairtin wi the lawest nummer. The atomic nummer o an element is the same as the nummer o electrons or protons in the atom.

In the periodic cairt the elements are arranged intae periods an groups. 

A row o elements athort the cairt is cried a period. Ilka period haes a nummer: frae 1 tae 7. Period 1 haes anely 2 elements in it: hydrogen an helium. Period 2 an Period 3 baith hae 8 elements. Ither periods are langer.

A raw o elements doun the cairt is cawed a group. Thare are 18 groups in the staundart periodic cairt. Ilka group haes a nummer: frae 1 tae 18. Elements in a group hae electrons arranged in similar weys, that gies thaim similar chemical properties (thay behave in similar weys). For ensaumple, group 18 is kent as the noble gases acause thay are aw gases an thay dinnae jyne wi ither atoms.