In a couple of sentences, describe the cognitive effects secondhand smoke can have upon children. (Site 1) They inhale more than 4,000 toxic substances, they are passive smokers, they involuntarily inhale the smoke from one or more smokers.
DANGER: respiratory diseases coughing, wheezing, bronchitis, recurrent ear infections, asthma, risk of tooth decay in children, some tobacco dependence, risk of becoming future smokers.
passive smoking also aggravates preexisting chronic respiratory diseases, cystic fibrosis and is associated with a risk of sudden infant death syndrome

oxygen is the first element in group 16 (via) of the periodic table. the periodic table is a chart that shows how chemical elements are related to each other. the elements in group 16 are said to belong to the chalcogen family. other elements in this group include  sulfur, selenium, tellurium,  and  polonium.  the name chalcogen comes from the greek word  chalkos,  meaning "ore." the first two members of the family, oxygen and sulfur, are found in most ores.

oxygen is by far the most abundant element in the earth's crust. nearly half of all the atoms in the earth are oxygen atoms. oxygen also makes up about one-fifth of the earth's atmosphere. nearly 90 percent of the weight of the oceans is due to oxygen. in addition, oxygen is thought to be the third most abundant element in the universe and in the solar system.