Differences Between Carbon-12 and Carbon-14

Differences Between Carbon-12 and Carbon-14 Carbon-12 and carbon-14 are two isotopes of the element carbon. The difference between carbon-12 and carbon-14 is the number of neutrons in each atom. The number given after the atom name (carbon) indicates the number of protons plus neutrons in an atom or ion. Atoms of both isotopes of carbon contain 6 protons. Atoms of carbon-12 have 6 neutrons, while atoms of carbon-14 contain 8 neutrons. A  neutral atom would have the same number of protons and electrons, so a neutral atom of carbon-12 or carbon-14 would have 6 electrons. Although neutrons do not carry an electrical charge, they have a  mass comparable to that of protons, so different isotopes have different atomic weight. Carbon-12 is lighter than carbon-14. Carbon  Isotopes and Radioactivity Because of the different number of neutrons, carbon-12 and carbon-14 differ with respect to radioactivity. Carbon-12 is a stable isotope. Carbon-14, on the other hand, undergoes radioactive decay: 146C → 147N 0-1e (half-life is 5720 years) Other Common Isotopes of Carbon The other common isotope of carbon is carbon-13. Carbon-13 has 6 protons, just like other carbon isotopes, but it has 7 neutrons. It is not radioactive. Although 15 isotopes of carbon are known, the natural form of the element consists of a mixture of only three of them: carbon-12, carbon-13, and carbon-14. Most of the atoms are carbon-12. Measuring the difference in the ratio between carbon-12 and carbon-14 is useful for dating the age of organic matter  since a living organism is exchanging carbon and maintaining a certain ratio of isotopes. In a diseased organism, there is no exchange of carbon, but the carbon-14 that is present undergoes radioactive decay, so over time, the isotope ratio becomes more and more different.

Definition of Indefinite Article

Definition of Indefinite Article An indefinite article, called an  artà ­culo  indefinido  in Spanish, makes a noun refer to a nonspecific item or items of its class. In English, there are only two indefinite articles, a and an. In Spanish, there are four indefinite articles,  un, una, unos, and unas. Spanish and English have different grammatical rules concerning when indefinite articles  are needed or should be omitted. Agreement in Number or Gender Matters In Spanish, number and gender make a difference. Is the word plural or singular? Is the word masculine or feminine? The Spanish indefinite article must agree with the gender and number of the noun that follows it. Singular Forms of the Indefinite Article There are two singular indefinite articles, un and una, translating to a or an.  Un is used when referring to a masculine word, for example, un  gato,  meaning, a cat. Una is used before a feminine word, as in una persona, meaning, a person. Plural Forms of the Indefinite Article There are two plural forms of indefinite articles in Spanish, unos  and unas, translating to a few or some. Unos is masculine. Unas is feminine. In this case, the correct form to use depends on the gender of the word being described,  for example, She is reading  some  books, can be translated to be  Ella lee  unos  libros.  Although a female is reading the books, the word being described is libros, which is a masculine word, therefore, the article uses the masculine form of the word. An example of unas  being used in a sentence would be,  Yo sà © unas palabras  en  espaà ±ol,  which means, I know a few words in Spanish. Although the word some is considered an indefinite article in Spanish, the word some is not classified as an indefinite article in English. Some is considered as an indefinite pronoun or a quantifier in English. Exceptions to the Rule With every language, there will always be exceptions to the rule. When a feminine singular noun begins with a stressed  ,  a, or  ha, the masculine indefinite article is used instead of the feminine indefinite article to aide in pronunciation. For example, the word,  guila, meaning, eagle, is a feminine word. When referring to an eagle, instead of saying una  guila, which sounds clunky in pronunciation, the grammar rule allows a speaker to say un  guila, which has a smoother flow. The plural form remains feminine because pronunciation is not affected when a speaker says,  unas  guilas. Similarly, the Spanish word for ax is hacha,  a feminine word. A speaker would say, un hacha, as the singular form and  unas hachas as the plural form.