Dividing line between metals and nonmetals

The dividing line between metals and nonmetals is a stair-shaped line on the periodic table which separates chemical elements into metals and nonmetals.

	1	2	...	12	13	14	15	16	17	18
	H									He
	Li	Be			B	C	N	O	F	Ne
	Na	Mg			Al	Si	P	S	Cl	Ar
	K	Ca	...	Zn	Ga	Ge	As	Se	Br	Kr
	Rb	Sr	...	Cd	In	Sn	Sb	Te	I	Xe
	Cs	Ba	...	Hg	Tl	Pb	Bi	Po	At	Rn
	Fr	Ra	...	Cn	Nh	Fl	Mc	Lv	Ts	Og
	An example of a periodic table metal–nonmetal dividing line, shown in the s- and p-blocks.

There is no formal definition of "metal" in chemistry. This line is a convention, and not a firm scientific rule. Most of the elements close to the line are called metalloids, because they have some things in common with metals and other things with nonmetals.