periodic table definition alkali metals definition chemistry

#Periodic table definition alkali metals definition chemistry plus

Watch this brief video about the periodic table and element groups, from Crash Course.

Oganesson completes the seventh period of the periodic table, so if anyone manages to synthesize element 119 (and the race to do so is already underway), it will loop around to start row eight in the alkali metal column.īecause of the cyclical nature created by the periodicity that gives the table its name, some chemists prefer to visualize Mendeleev's table as a circle. Many chemists expect oganesson (previously designated ' ununoctium'), one of the four newly named elements, to share these characteristics however, because this element has a half-life measuring in the milliseconds, no one has been able to test it directly.

Noble gases: Colorless, odorless and almost completely nonreactive, the inert, or noble gases round out the table in Group 18. The table salt in your kitchen, for example, is a marriage between the alkali metal sodium and the halogen chlorine. The halogens are quite chemically reactive and tend to pair up with alkali metals to produce various types of salt. Halogens: The top four elements of Group 17, from fluorine (F) through astatine (At), represent one of two subsets of the nonmetals. These include carbon (C), nitrogen (N), phosphorus (P), oxygen (O), sulfur (S) and selenium (Se).

#Periodic table definition alkali metals definition chemistry plus

Nonmetals: Everything else to the upper right of the staircase - plus hydrogen (H), stranded way back in Group 1 - is a nonmetal. Metalloids are also called 'semimetals' or 'poor metals.' These elements sometimes behave as semiconductors (B, Si, Ge) rather than as conductors. They form the staircase that represents the gradual transition from metals to nonmetals. Metalloids: The metalloids are boron (B), silicon (Si), germanium (Ge), arsenic (As), antimony (Sb), tellurium (Te) and polonium (Po). The post-transition metals cluster to the lower left of this line. Many periodic tables will feature a bolded 'staircase' line below the diagonal connecting boron with astatine.

These elements have some of the classic characteristics of the transition metals, but they tend to be softer and conduct more poorly than other transition metals. The post-transition metals are aluminum (Al), gallium (Ga), indium (In), thallium (Tl), tin (Sn), lead (Pb) and bismuth (Bi), and they span Group 13 to Group 17. Post-transition metals: Ahead of the jump into the nonmetal world, shared characteristics aren't neatly divided along vertical group lines. Many of the greatest hits of the metal world - including gold, silver, iron and platinum - live here. Hard but malleable, shiny, and possessing good conductivity, these elements are what you typically think of when you hear the word metal. Transition metals: Returning to the main body of the table, the remainder of Groups 3 through 12 represent the rest of the transition metals. The actinides and the lanthanides together form a group called the inner transition metals. Of these elements, only thorium (Th) and uranium (U) occur naturally on Earth in substantial amounts. The elements in this group have a silvery white color and tarnish on contact with air.Īctinides: The actinides line the bottom row of the island and comprise elements 89, actinium (Ac), through 103, lawrencium (Lr). This is the lanthanides, elements 57 through 71 - lanthanum (La) to lutetium (Lu).

Lanthanides: The third group is much too long to fit into the third column, so it is broken out and flipped sideways to become the top row of the island that floats at the bottom of the table. Their chemical reactions typically occur more slowly and produce less heat compared to the alkali metals. But they're not as reactive as the alkali metals. Each of these elements has two electrons in its outermost energy level, which makes the alkaline earths reactive enough that they're rarely found alone in nature. Hydrogen, with its single electron, also lives in Group 1, but the gas is considered a nonmetal.Īlkaline-earth metals: The alkaline-earth metals make up Group 2 of the periodic table, from beryllium (Be) through radium (Ra). They are also extremely reactive and will burst into flame or even explode on contact with water, so chemists store them in oils or inert gases. Shiny and soft enough to cut with a knife, these metals start with lithium (Li) and end with francium (Fr). The periodic table of elements is arranged into several broad groups (Image credit: Future) Groups of the Periodic tableĪlkali metals: The alkali metals make up most of Group 1, the table's first column.