Krypton

The third period contains eight elements: sodium, magnesium, aluminium, silicon, phosphorus, sulfur, chlorine, and argon. The first two, sodium and magnesium, are members of the s-block of the periodic table, while the others are members of the p-block….Period 3 element.

Radon

noble gas xenon

I’m lighter than air but a million men can’t lift me. What am I? A bubble.

The balloon loaded up with air from the lungs falls to the ground gradually because the balloon is denser than the air. The combined density of the ballon itself (the thin rubber sheet) and the air inside is heavier than the surrounding air.

Hydrogen. Hydrogen is the lightest and most common element in the universe, consisting of just a single proton and a single electron, with the chemical symbol H.

Hydrogen is the lightest element of the periodic table, thus, hydrogen gas is the lightest gas. The atomic mass of hydrogen gas (H2) is twice the mass of hydrogen element (H). The atomic mass of the hydrogen element is 1 gram.

The chemical formula of helium is He because helium cannot form diatomic molecule like nitrogen form N2 and Oxygen form O2 but helium cannot form He2… According to molecular orbital theory when two Atomic orbitals of (1s2) two helium atoms combine they produce two molecular orbitals.

Methane is lighter than air, colourless and, despite what you might think considering animals burp it out, odourless.

Sewage gas is heavier than atmospheric gas and it “sinks” to the lowest level in the house or in a room. The sewage gas smells are caused because somewhere within or outside of the house, the rotten egg smell is not being vented and so it starts to accumulate.

For as well as emitting methane, trees also absorb the gas. Many emit methane close to their base while absorbing it further aloft. There is an urgent need to include tree emissions in greenhouse gas emissions inventories. The bottom line, says Pangala, is that almost all trees can both emit and absorb methane.

Why Is Methane Gas Dangerous? Methane is not generally considered a toxic gas, however it is extremely flammable even in low concentrations when mixed with other chemicals – it is also an asphyxiant as it will displace oxygen. This is particularly dangerous in confined spaces working.

In severe cases, there may be changes in breathing and heart rate, balance problems, numbness, and unconsciousness. If exposure is large or continues for a longer period it can kill. Skin or eye contact with liquefied methane released under pressure may cause frostbite.

Methane can explode at concentrations of 50,000 ppm or more (a level of 5 per cent).