Rosenberg MJ, Meyers A, Roy V. Efficacy, cycle control, and side effects of low- and lower-dose oral contraceptives: a randomized trial of 20 micrograms and 35 micrograms estrogen preparations. Contraception 1999; 60:321. Gallo MF, Nanda K, Grimes DA, Schulz KF. 20 mcg versus >20 mcg estrogen combined oral contraceptives for contraception. Cochrane Database Syst Rev 2005; :CD003989. Bachmann G, Korner P. Bleeding patterns associated with oral contraceptive use: a review of the literature.
A molecule is formed from two or more atoms of a single element. An example is h2o. two hydrogen atoms and one oxygen atom forming a molecule of water! This question is archived.
Elements are composed of atoms, which are extremely small. All atoms of a given element have the same chemical properties and contain the same number of protons. Compounds are formed by the chemical combination of two or more different kinds of atoms. (Whole numbers only) Atoms are the units of chemical change.