April 17, 2017
What Makes an Element?
All elements have some of the same structural components. Each atom of an element, no matter which one we want to look at, has three main components: electrons, protons and neutrons. Protons are positive particles and neutrons are neutral particles, though both of them are in the center of the atom, forming the nucleus. Electrons, meanwhile, have a negative charge and are outside the nucleus. All of these particles, the electrons, protons, and neutrons, are collectively called subatomic particles and they determine the size, charge, physical and chemical properties which determine the unique identity all elements we know! Illustrated is a rendering of an atom of carbon and an atom of neon.
However, it's not enough to know that elements have electrons, protons, and neutrons. For two atoms to be the same element, they must have the same number of protons which will also mean they have the same atomic number. Another key characteristic is atomic weight. Atomic weight is a reflection of the weight of the total number of neutrons and protons of the atom. These values are listed systematically in a table of elements which will be described later.
Let's consider carbon as our example of a typical atom. Carbon is very abundant in nature and its atomic weight was actually the standard for measuring the atomic weight of all other elements. Carbon's atomic number is 6, which means it has 6 protons. It also has 6 electrons and 6 neutrons. Its atomic weight is 12.01.
It is called the periodic table of elements because elements with similar properties occur at regular intervals - periodically.
The elements are arranged in order of atomic number (proton number) so that very similar elements end up in vertical columns called groups AND they have the same number of outer electrons in the highest level containing electrons (except H and He) which gives them very similar chemical properties.
Over 100 elements are now known, but only 92 elements of the periodic table are found naturally on Earth as elements or (usually) compounds.
Most elements are metals on the left and lower parts of the periodic table. Non-metals are on the right and towards the top of the periodic table. The thick diagonal zig–zag black line shows the main division between metals on the left of the periodic table and non–metals on the right of the periodic table. However, note that the metallic elements and non–metallic elements adjacent to this zig–zag line can show a 'mixture' of properties.
From a working knowledge of the periodic table you should be able to predict the number of outer electrons (e.g. Groups 1–7) possible compound formulae, reactions and symbol equations and the probable reactivity of elements from their positions in the periodic table. This is especially so for e.g. Group 1 Alkali Metals and the Group 7 halogens.
Comparison chart
| Compound | Element | |
|---|---|---|
| Meaning | A compound contains atoms of different elements chemically combined together in a fixed ratio. | An element is a pure chemical substance made of same type of atom. |
| Distinguishing Feature | Compounds contain different elements in a fixed ratio arranged in a defined manner through chemical bonds. | Elements are distinguished by their atomic number (number of protons in their nucleus). |
| Ability to Breakdown | A compound can be separated into simpler substances by chemical methods/reactions. | Elements cannot be broken down into simpler substances by chemical reactions. |
| Types | The list of compounds is endless. | There are about 117 elements that have been observed. Can be classified as metal, non-metal or metalloid. |
| Representation | A compound is represented using a formula. | An element is represented using symbols. |
| Examples | Water (H2O), Sodium chloride (NaCl), Sodium bicarbonate (NaHCO3) etc. | Iron, copper, silver, gold, nickel etc. |
source : http://www.diffen.com/difference/Compound_vs_Element
http://study.com/academy/lesson/what-is-an-element-in-chemistry.html
Please explain about halogen class!
ReplyDeletehalogen elements are a group in the periodic table consisting of five chemically related elements: fluorine (F), chlorine (Cl), bromine (Br), iodine (I), and astatine (At). The artificially created element 117 (tennessine, Ts) may also be a halogen. In the modern IUPAC nomenclature, this group is known as group 17. The symbol X is often used generically to refer to any halogen.
DeleteThe name 'halogen' means 'salt-producing'. When halogens react with metals they produce a wide range of salts, including calcium fluoride, sodium chloride (common table salt), silver bromide and potassium iodide.
The group of halogens is the only periodic table group that contains elements in three of the four main states of matter at standard temperature and pressure. All of the halogens form acids when bonded to hydrogen. Most halogens are typically produced from minerals or salts. The middle halogens, that is chlorine, bromine and iodine, are often used as disinfectants. Organobromides are the most important class of flame retardants. Elemental halogens are dangerously to potentially lethally toxic.
Explain example of element in everyday life!
ReplyDeletegold
Deleteiron
HHO
hydrogen etc
Please compare element between hidrogen and sulfur!
ReplyDeleteHydrogen is a chemical element with chemical symbol H and atomic number 1. With a standard atomic weight of circa 1.008, hydrogen is the lightest element on the periodic table. Its monatomic form (H) is the most abundant chemical substance in the Universe, constituting roughly 75% of all baryonic mass .
Deleteand then sulfur
is a chemical element with symbol S and atomic number 16. It is abundant, multivalent, and nonmetallic. Under normal conditions, sulfur atoms form cyclic octatomic molecules with a chemical formula S8. Elemental sulfur is a bright yellow crystalline solid at room temperature. Chemically, sulfur reacts with all elements except for gold, platinum, iridium, tellurium, and the noble gases.
thanks for your question
Give the distinction between elements of one class
ReplyDeleteHydrogen is the smallest chemical element because it consists of only one proton in its nucleus. Its symbol is H, and its atomic number is 1. It has an average atomic weight of 1.0079 amu, making it the lightest element. Hydrogen is the most abundant chemical substance in the universe, especially in stars and gas giant planets. However, monoatomic hydrogen is rare on Earth is rare due to its propensity to form covalent bonds with most elements.
Deleteand then K (potassium )
Potassium is the second least dense metal after lithium. It is a soft solid with a low melting point, and can be easily cut with a knife. Freshly cut potassium is silvery in appearance, but it begins to tarnish toward gray immediately on exposure to air. In a flame test, potassium and its compounds emit a lilac color with a peak emission wavelength of 766.5 nanometers.
Please explain the comparison of hydrogen and helium balloons?
ReplyDeleteThe densities of interest are...
DeleteAir (fluid): 1.2 kg/(m^3)
Helium (contents): 0.0899 kg/(m^3)
Hydrogen (contents): 0.1786 kg/(m^3)
Helium has an atomic mass of about four times that of hydrogen. But it does not form a diatomic molecule like hydrgen (H2) does. So it's density is only twice that of hydrogen, rather than four times. So the answer to your question is that, at STP,
The CONTENTS of a hydrogen filled ballon will give a net bouyant force of about:(9.8)(1.2kg - 0.0899kg)/(m^3) = 10.0N/(m^3) ---> about 2.44 lb./(m^3)
The CONTENTS of a helium filled ballon will givea net bouyant force of:(9.8)(1.2kg - 0.1786kg)/(m^3) = 10.0N/(m^3) ---> about 2.25 lb./(m^3)
The hydrogen filled ballon gives about 9% more net bouyant force.
Remember that temperature and pressure both dramatically affect actual bouyant force.
Hydrogen and helium have less weight than a similar volume of air at the same pressure. That means the buoyant force on them, which is just enough to hold up air, is more than enough to hold up the balloons, and theyhave to be tethered down.