2015-10-13
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Notice in Figure 1 above how each element has a number associated with it? That number is the atomic number — the number of protons in the nucleus of an atom of a particular element. For example, carbon (the letter C in the periodic table) has six protons in the nucleus of one atom, so its atomic number is 6. Periodic law states that the properties of elements are a periodic function of their atomic numbers. In other words, when elements are arranged by their atomic number, they form groups with similar properties. The number of electrons in one atom of an element is also equal to the atomic number because atoms are neutral (the positively charged particles are offset by the negatively charged particles one for one).
Of all the elements in the periodic table, living things use only a handful. The four most common elements found in living things are hydrogen, carbon, nitrogen, and oxygen, all of which are found in air, plants, and water. (Several other elements exist in smaller amounts in organisms, including sodium, magnesium, phosphorus, sulfur, chlorine, potassium, and calcium.)
Most often, the elements sodium, magnesium, chlorine, potassium, and calcium circulate in the body as electrolytes, substances that release ions when they break apart in water. For instance, when in the “water” of the body, sodium chloride (NaCl) breaks apart into the ions Na+and Cl–, which are then used either in organs such as the heart or in cellular processes.
Ex. 9. Choose the correct variant for each sentence using Video #1.
1. Today we know that it is the /billeting/layout/arrangement of electrons inside each atom that determine its chemical behavior/properties / features. And similar arrangements lead to similar properties// features/behavior.
2. All of the elements in the table are arranged into groups based on different meaning/values/significance of l. Elements in a given column have their outer electrons in similarly shaped orbitals, and this means they have similar chemical properties.
3. In a given group, n increases by one for each row in the table. So the outward/external/outer electrons in elements directly below other elements have more energy and are less tightly bound/attached to the atom.
LESSON 2. MOLECULES AND BONDS
Ex. 10. Translate the following text into your native language.
