Hydrogen is placed in Group 1 of the periodic table because it has a single electron in its outer shell, similar to the other alkali metals. 1 It also has similar chemical properties to the alkali metals, such as its reactivity with water and oxygen. 2
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Key Takeaways: Why is Hydrogen in Group 1?
- Hydrogen is placed in Group 1 of the periodic table due to its one electron in the outer shell and similar properties to the alkali metals. It tends to lose its electron to form a positive ion and reacts similarly to other Group 1 elements. However, hydrogen is less reactive and a gas at room temperature.
- It is not an alkali metal as it can either lose or share its one electron and tends to form covalent compounds instead of ionic compounds.
- Hydrogen is not placed in Group 17 as it does not have the same properties as halogens and has a different electronegativity, forming covalent bonds with other elements.
Explanation: Why is hydrogen in group 1?
Hydrogen is placed in Group 1 of the periodic table because it has similar properties to the other elements in that group. 3
These properties include:
- One electron in the outer shell. Hydrogen has one electron in its outer shell, just like the other elements in Group 1.
- A tendency to lose an electron. Hydrogen is a very reactive element and it tends to lose its one electron to form a positive ion (H+). 4 This is similar to the other elements in Group 1, which also tend to lose their outer electron to form positive ions. 5 6
- A similar chemical behavior. Hydrogen reacts with other elements in similar ways to the other elements in Group 1. For example, hydrogen reacts with oxygen to form water, 7 just like the other elements in Group 1 react with oxygen to form hydroxides. 8
Although hydrogen has some similarities to the other elements in Group 1, it also has some important differences.
For example, hydrogen is a gas at room temperature, while the other elements in Group 1 are metals. 9 10 Hydrogen is also much less reactive than the other elements in Group 1.
Overall, hydrogen is placed in Group 1 of the periodic table because it has more similarities to the other elements in that group than it does to the elements in other groups.
Why is hydrogen not an alkali metal?
Hydrogen is not an alkali metal because it has some properties that are different from the alkali metals.
Here are the main differences between hydrogen and the alkali metals, presented in tabular form:
| Property | Hydrogen | Alkali Metals |
| Ionization Energy | Low | Very Low |
| Reactivity | Less Reactive | Highly Reactive |
| Electronegativity | Low | Very Low |
| Melting and Boiling Point | Low 11 | High |
| Physical State | Gas | Solid |
| Forms covalent bonds? | Yes | No |
Alkali metals have one electron in their outermost shell and a low ionization energy, which makes it easier for them to lose that electron and form positive ions.
In contrast, hydrogen has only one electron, which it can either lose or share with other atoms to form covalent bonds.
Alkali metals are highly reactive and easily form ionic compounds with non-metals, while hydrogen is less reactive and tends to form covalent compounds. 12 13
Alkali metals have low electronegativity, melting and boiling points, and are usually solids at room temperature, while hydrogen is a gas at room temperature and has a low electronegativity. 14
Why is hydrogen not placed in group 17?
Hydrogen is not placed in group 17 of the periodic table because it does not have the same properties as the halogens in that group. The halogens are all nonmetals and have a strong tendency to gain electrons to form negative ions. Hydrogen, on the other hand, can either lose or gain electrons, depending on the reaction. 15
Hydrogen has a different electronegativity than the halogens, which is a measure of how strongly an atom attracts electrons. Hydrogen has an electronegativity of 2.20, while the halogens have electronegativities of 3.00-4.00. 16 This means that hydrogen is not as electronegative as the halogens and is not as likely to gain electrons.
Furthermore, hydrogen forms covalent bonds with other elements, while the halogens form ionic bonds. Covalent bonds are formed when atoms share electrons, while ionic bonds are formed when one atom donates an electron to another atom. Hydrogen is more likely to form covalent bonds than ionic bonds, which is another reason why it is not placed in group 17.
Overall, hydrogen has few properties that are similar to the halogens, but it also has major important differences. These differences are why hydrogen is not placed in group 17 of the periodic table.
Further reading
Is Hydrogen Reactive?
Why is Hydrogen Diatomic?
Is Hydrogen a Compound?
Why is Hydrogen Flammable?
Does Hydrogen have Neutrons?
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References
- Hydrogen adopts alkali metal position. (2013, November 7). Hydrogen Adopts Alkali Metal Position | Research | Chemistry World. https://www.chemistryworld.com/news/hydrogen-adopts-alkali-metal-position/6769.article
- 6.9: Hydrogen and Alkali Metals. (2016, June 27). Chemistry LibreTexts. https://chem.libretexts.org/Bookshelves/Introductory_Chemistry/Introductory_Chemistry_(CK-12)/06%3A_The_Periodic_Table/6.09%3A_Hydrogen_and_Alkali_Metals
- Foundation, C. (n.d.). CK12-Foundation. CK12-Foundation. https://flexbooks.ck12.org/cbook/ck-12-chemistry-flexbook-2.0/section/6.9/primary/lesson/hydrogen-and-alkali-metals-chem/
- Hydrogen ion – Wikipedia. (2014, October 1). Hydrogen Ion – Wikipedia. https://en.wikipedia.org/wiki/Hydrogen_ion
- hyperphysics.phy-astr.gsu.edu http://hyperphysics.phy-astr.gsu.edu/hbase/pertab/alkmet.html
- Group IA. (n.d.). Group IA. https://chemed.chem.purdue.edu/genchem/topicreview/bp/ch9/alkali.php
- Scientists discover new way to make water | Chemistry at Illinois. (n.d.). Scientists Discover New Way to Make Water | Chemistry at Illinois. https://chemistry.illinois.edu/news/2007-12-31/scientists-discover-new-way-make-water
- Information on Alkali Metals – Stanford Environmental Health & Safety. (n.d.). Information on Alkali Metals – Stanford Environmental Health & Safety. https://ehs.stanford.edu/reference/information-alkali-metals
- Hydrogen explained – U.S. Energy Information Administration (EIA). (2023, May 4). Hydrogen Explained – U.S. Energy Information Administration (EIA). https://www.eia.gov/energyexplained/hydrogen/
- 8.3: Group 1, The Alkali Metals. (2019, May 22). Chemistry LibreTexts. https://chem.libretexts.org/Bookshelves/Inorganic_Chemistry/Inorganic_Chemistry_(LibreTexts)/08%3A_Chemistry_of_the_Main_Group_Elements/8.03%3A_Group_1_The_Alkali_Metals
- Appendix 2: The Elements: Symbols, Melting Points, Boiling Points, Densities, and Electronegativities. (n.d.). Ionic Compounds, 169–170. https://doi.org/10.1002/0470075104.app2
- Hawaii.edu https://www.manoa.hawaii.edu/exploringourfluidearth/chemical/chemistry-and-seawater/covalent-compounds
- Boudreaux, K. A. (n.d.). The Parts of the Periodic Table. The Parts of the Periodic Table. https://www.angelo.edu/faculty/kboudrea/periodic/periodic_main1.htm
- Allred, A. (1961, June). Electronegativity values from thermochemical data. Journal of Inorganic and Nuclear Chemistry, 17(3–4), 215–221. https://doi.org/10.1016/0022-1902(61)80142-5
- 22.2: Hydrogen. (2017, August 29). Chemistry LibreTexts. https://chem.libretexts.org/Courses/University_of_Missouri/MU%3A__1330H_(Keller)/22%3A_Chemistry_of_the_Nonmetals/22.02%3A_Hydrogen
- Electronegativities of the elements (data page) – Wikipedia. (n.d.). Electronegativities of the Elements (Data Page) – Wikipedia. https://en.wikipedia.org/wiki/Electronegativities_of_the_elements_(data_page)
