first class L2

Unit 2 Chemistry
If you look chemistry up in Webster s Dictionary, you ll see: "chem·is·try.
1. the science that systematically studies the composition, properties, and activity of organic and inorganic substances and various elementary forms of matter.
2. Chemical properties, reactions, phenomena, etc.: the chemistry of carbon.
My definition is the short and sweet, "scientific study of matter, its properties, and interactions with other matter and with energy". An important point to remember is that chemistry is a science, which means its procedures are systematic and reproducible and its hypotheses are tested using the scientific method. Chemists, scientists who study chemistry, examine the properties and composition of matter and the interactions between substances. Chemistry is closely related to physics and to biology. As is true for other sciences, mathematics is an essential tool for the study of chemistry.
Q: How many meanings of the word chemistry are mentioned in the article?

Q: Which branches of science are, according to the article, closely related to chemistry? Do you agree?

Q: Why, according to the article, is chemistry a science? What criteria are mentioned?
Q: Do you think that mathematics is an essential tool for the study of chemistry, as the article says? Do you as the students of chemistry need to study mathematics?
Q: Find the examples of plural words in the text.
singular ending plural ending
synthesis syntheses
hypothesis ____________
phenomenon phenomena
criterion ____________
Some of these words have double plural form: formula formulae
formulas
Some words follow the English rules: dogma dogmas


Q: Read the text and fill in the gaps with the following expressions in appropriate forms. Use each expression only once.
(proton, neutron, element, electron, atomic nucleus, molecule, cation, anion, chemical compound, chemical bonds, ion, molecule, atomic number)
An atom is a collection of matter consisting of a positively charged core ( the _ atomic nucleus ) which contains proton and neutron and which maintains a number of
electrons to balance the positive charge in the nucleus. The atom is also the smallest portion into which an element can be divided and still retain its properties, made up of a dense, positively charged nucleus surrounded by a system of electron.
The most basic chemical substances are the chemical elements. They are building blocks of all other substances. An element is a class of atoms which have the same number of protons in the nucleus. This number is known as the atomic number of the element. For example, all atoms with 6 protons in their nuclei are atoms of the chemical element carbon, and all atoms with 92 protons in their nuclei are atoms of the element uranium. Each chemical element is made up of only one kind of atom. The atoms of one element differ from those of all other elements. Chemists use letters of the alphabet as symbols for the elements. In total, 117 elements have been observed as of 2007, of which 94 occur naturally on Earth. Others have been produced artificially.
An Ion is an atom or a molecule that has lost or gained one or more electrons.
Positively charged cation (e.g. sodium cation Na+) and negatively charged anion(e.g. chloride Cl?) can form neutral salts (e.g. sodium chloride NaCl).
Electrical forces at the atomic level create chemical bonds that join two or more atoms together, forming molecule. Some molecules consist of atoms of a single element.
Oxygen molecules, for example, are made up of two oxygen atoms. Chemists represent the oxygen molecule O2. The 2 indicates the number of atoms in the molecule.

Q: Put the following expressions into correct places in the Periodic Table.
Then read the text about the Periodic Table and answer question.
atomic weight, name, atomic number, group, row, alkali metals, halogens, lanthanides, columns

Periodic table
The most convenient presentation of the chemical elements is in the periodic table of the
chemical elements, which groups elements by atomic number Due to its ingenious
arrangement, columns, or group , and row, or periods, of elements in the
table either share several chemical properties, or follow a certain trend in characteristics such as
atomic radius, electronegativity, electron affinity, etc.
The main value of the periodic table is the ability to predict the chemical properties of an
element based on its location on the table. The properties vary differently when moving vertically
along the columns of the table, than when moving horizontally along the row.
The periodic table was first devised in 1869 by the Russian chemist Dmitri Mendeleev.
Mendeleev intended the table to illustrate recurring ("periodic") trends in the properties of the
elements. The layout of the table has been refined and extended over time, as new elements have
been discovered, and new theoretical models have been developed to explain chemical behaviour.
Various layouts are possible to emphasize different aspects of behaviour; the most common forms,
however, are still quite similar to Mendeleev s original design.
Q: What are the synonyms of the following words used in the article?
ingenious
location
recurring
to refine
to emphasize
unique