Earth

=== Chemical composition ===
{{See also|Abundance of elements on Earth}}

[[Earth mass|Earth's mass]] is approximately {{val|5.97|e=24|ul=kg}} (5,970 [[yottagram|Yg]]). It is composed mostly of iron (32.1% [[Mass fraction (chemistry)|by mass]]), [[oxygen]] (30.1%), [[silicon]] (15.1%), [[magnesium]] (13.9%), [[sulfur]] (2.9%), [[nickel]] (1.8%), [[calcium]] (1.5%), and [[aluminium]] (1.4%), with the remaining 1.2% consisting of trace amounts of other elements. Due to [[Planetary differentiation#Gravitational separation|gravitational separation]], the core is primarily composed of the denser elements: iron (88.8%), with smaller amounts of nickel (5.8%), sulfur (4.5%), and less than 1% trace elements.<ref name="pnas71_12_6973" /><ref name="comp" /> The most common rock constituents of the crust are [[oxide]]s. Over 99% of the [[Earth's crust|crust]] is composed of various oxides of eleven elements, principally oxides containing silicon (the [[silicate mineral]]s), aluminium, iron, calcium, magnesium, potassium, or sodium.<ref name="brown_mussett1981" /><ref name="pnas71_12_6973" />