Why heart is placed on the left hand side

The heart initially appears in the midline and we know that it moves to the left. How? Because there are cells that, once the cardiac primordium is formed, arrive from both sides of the embryo towards the center

hydrogen is a compound or a single element and a element is a pure substence that cannot be separated into simpler subtances

clorine is a compound its a chemical substance that forms when two or more different elements combine

so both hydrogen and clorine are compounds

oxygen = 21% of the atmosphere

nitrogen = 78%

carbon dioxide = 0.1%

argon =0.934%