Metals Flashcards
To learn the matter
The structur of matter !!!
Definitions !
Matter: the substances of which everything is made.
Elements: all matter is made from one or more of the known elements.
Atom: the smallest quantity of a given element that retains the properties of that element.
An Atom consist of a nucleus (protons and neutrons), coupled with its orbiting electrons.
The atomic number: the number of protons in the nucleus of an atom.
Elements with 6 protons are always carbon, and all forms of carbon have exactly 6 protons
Atomic mass: protons plus neutrons.
More defintions !!!
Isotopes: carbon nuclei with 8 neutrons and a mass number of 14 (14C).
14C is a radioisotope, which is an isotope with an unstable nucleus that emits radiation until it achieves a stable state.
Molar mass of the element: The atomic weight, measured in grams per mole (g/mol). In 1 atomic weight (12.011 g for carbon) there is 1 mole of atoms (6.023 × 1023 atoms) .
The periodic table !!!
Dimitri Mendeleev,a Russian chemist in the mid-19th century, recognized that when all of the known elements were arranged in order of atomic weight, certain patterns of reactivity became apparent = the Periodic Table of the Elements.
In general, only electrons in unfilled shells, or valence shells, are involved in chemical reactions.
The periodic table !
- Broadly, the periodic table is divided into metals and nonmetals.
- metals (left side, conduct electricity) and nonmetals (right side, dull, fragile)
- both are divided by metalloids (intermediate between the two).
- Each column of elements is termed a family or group, and each raw is a period.
physicochemical properties in teh periodic table !!
Toxicity of each element depends on the physicochemical properties, which may be predicted by their location on the periodic table.
Lithium for example !!
Li+ may mimic K+ and enter neurons through K+ channels, where it serves as a poor substrate for the repolarizing Na+-K+-ATPase. Thus, Li+ interferes with cellular K+ homeostasis and alters neuronal repolarization accounting for the neuroexcitability manifesting as tremor.
Metals are chemical elements that possess three general properties :
(1) they are a good conductor of heat and electricity
(2) they are able to form cations
(3) they can combine with nonmetals through ionic bonds.
heavy or toxic metals !!
In clinical toxicology, the following metals, noted in ascending atomic weight, are usually considered under the concept of “heavy” or “toxic” metal poisoning: beryllium, vanadium, cadmium, barium, osmium, mercury, thallium, and lead, with lead and mercury being the metals most clinically significant concerning human poisoning.
the term should be reserved to describe only those metals in the lower period of the periodic table.
particularly those with atomic masses greater than 200.
Also, because the chemistry of metals varies dramatically based on the chemical form (ie, organic, inorganic, or elemental), as well as the charge on the metal ion, prediction of the clinical effects of a particular metal is often difficult.
Metalloids !!!
chemical elements with properties intermediate to those of metals and nonmetals. Although there is no precise definition, metalloids tend to have these two general properties: (1) they are semiconductors of electricity, and (2) they form amphoteric oxides.
share many physical properties with the metals, they are differentiated because of their propensity to form compounds with both metals and the nonmetals carbon, nitrogen, or oxygen. Thus, metalloids may be either oxidized or reduced in chemical reactions.
Arsenic !!
pentavalent arsenite (As5+) form or the trivalent arsenate (As3+) form. Trivalent form is a nucleophilic, binding to sulfhydryl groups and interfere with enzymatic functions.
Non Metals
(C, N, P, O, S, Se, halogens) are highly electronegative and, unlike the metals, may be toxic in either their compounded or their elemental form.
Halogens
(F, Cl, Br, I, At) carry the suffix -ine (eg, Cl2, chlorine), are strong oxidizing agents and they form halides (eg, Cl−, chloride) by abstracting electrons from less electronegative elements. These are reducing agents. All hydrogen halides except HF (hydrogen fluoride) ionize nearly completely in water to release H+ and are considered strong acids.
Group 0 / inert gases
inert gases (Noble gases): (He, Ne, Ar, Kr, Xe, Rn), maintain completed valence shells and are unreactive (simple asphyxiants).
