The chemical signs and the meaning

Flame: Flammable materials or substances liable to self ignite when exposed to water or air (pyrophoric), or which emit flammable gas.

Flame

Flame

Exclamation Mark: An immediate skin, eye or respiratory tract irritant, or narcotic.

Exclamation Mark

Exclamation Mark

Gas Cylinder: Gases stored under pressure, such as ammonia or liquid nitrogen.

Gas Cylinder

Gas Cylinder

Corrosion: Materials causing skin corrosion/burns or eye damage on contact, or that are corrosive to metals.

Corrosion

Corrosion

Exploding Bomb: Explosives, including organic peroxides and highly unstable material at risk of exploding even without exposure to air (self-reactives).

Exploding Bomb

Exploding Bomb

Flame Over Circle: Identifies oxidizers. Oxidizers are chemicals that facilitate burning or make fires burn hotter and longer.

Flame Over Circle

Flame Over Circle

Skull and Crossbones: Substances, such as poisons and highly concentrated acids, which have an immediate and severe toxic effect (acute toxicity).  

Skull and Crossbones

Skull and Crossbones

Environmental Hazard: Chemicals toxic to aquatic wildlife. (Non-Mandatory)

Explanation:

atomic mass = 39

number of neutrons = 20

number of protons= 19

electronic configuration = 1s2 2s2 2p6 3s2 3p6 4s1

the number of electron in first shell = 2

number of electrons in n=3 shell = 8