The Password Game: Solving Rule 18 with Atomic Numbers

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Find the elements whose atomic numbers add up to 200

Co-authored by A.J. Jacobs and Hannah Dillon

Last Updated: August 27, 2025 Fact Checked

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How to Beat Rule 18

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Rule 18 Solution

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All Atomic Numbers

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Considerations for Other Rules

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Video

In the Password Game, Rule 18 is one of the more difficult rules to get through, but thankfully, it's not impossible! In this article, we go over how to beat Rule 18 and what you need to know to get past it, as well as some tips on how to write a solution. We also include a chart of all of the elements and their corresponding atomic numbers, as well as a list of considerations for other rules in the game that might get messed up due to Rule 18. Keep reading to learn more!

Beating Rule 18 in the Password Game

In your password, you'll see letters highlighted when you reach Rule 18. These are the element symbols currently in the password, and they correlate to an atomic number. All of the elements in your password must have atomic numbers that add up to 200 (such as Og and Pb, which correlate to 118 and 82).

Section 1 of 4:

How to Beat Rule 18

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The atomic number of all elements must add up to 200. When you get to Rule 18, you might see some letters or letter combos highlighted in your password. The letters highlighted correspond to one- or two-letter element symbols (such as O for oxygen, He for helium, Ir for iridium, etc.). Each of these elements has an atomic weight, and you must include a combination of elements that have atomic numbers that add up to 200.^{[1]
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- The best way to get through this rule is to avoid capital letters in your password as much as possible, except where required.
- The elemental symbols you choose should ideally not start with a Roman numeral (I, V, X, L, C, D, or M) and should not contain any vowels, to avoid messing up later rules.
- Since Rule 12 requires you to have a two-letter symbol for an element from the periodic table, you'll need to have at least one two-letter symbol in your password to begin with.

Section 2 of 4:

Rule 18 Solution

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There's not one easy solution for Rule 18. Since the contents of your password might vary depending on how you've completed the other rules in the game, there's no singular easy answer for Rule 18.
- One way to get through this rule is to avoid having any other element symbols in your password and type something like OgPb, which is Oganesson (118) and Lead (82), since 118 + 82 = 200.
- Alternatively, you can add up the atomic numbers for the elements already in your password, find an element that has an atomic number that matches the remainder, and add that to your password. Use the chart below to find the element with the appropriate atomic number.
  - For example, if you already have In (Indium), which has an atomic number of 49, Ar (argon), which has an atomic number of 18, and No (nobelium), which has an atomic number of 102, in your password, you'd do the following calculations:
    - 49 + 18 + 102 = 169
    - 200 - 169 = 31
    - You'd then add Ga (gallium) to your password, since gallium has an atomic number of 31.

Section 3 of 4:

All Atomic Numbers

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Element	Element Symbol	Atomic Number
Hydrogen	H	1
Helium	He	2
Lithium	Li	3
Beryllium	Be	4
Boron	B	5
Carbon	C	6
Nitrogen	N	7
Oxygen	O	8
Fluorine	F	9
Neon	Ne	10
Sodium	Na	11
Magnesium	Mg	12
Aluminium	Al	13
Silicon	Si	14
Phosphorus	P	15
Sulfur	S	16
Chlorine	Cl	17
Argon	Ar	18
Potassium	K	19
Calcium	Ca	20
Scandium	Sc	21
Titanium	Ti	22
Vanadium	V	23
Chromium	Cr	24
Manganese	Mn	25
Iron	Fe	26
Cobalt	Co	27
Nickel	Ni	28
Copper	Cu	29
Zinc	Zn	30
Gallium	Ga	31
Germanium	Ge	32
Arsenic	As	33
Selenium	Se	34
Bromine	Br	35
Krypton	Kr	36
Rubidium	Rb	37
Strontium	Sr	38
Yttrium	Y	39
Zirconium	Zr	40
Niobium	Nb	41
Molybdenum	Mo	42
Technetium	Tc	43
Ruthenium	Ru	44
Rhodium	Rh	45
Palladium	Pd	46
Silver	Ag	47
Cadmium	Cd	48
Indium	In	49
Tin	Sn	50
Antimony	Sb	51
Tellurium	Te	52
Iodine	I	53
Xenon	Xe	54
Cesium	Cs	55
Barium	Ba	56
Lanthanum	La	57
Cerium	Ce	58
Praseodymium	Pr	59
Neodymium	Nd	60
Promethium	Pm	61
Samarium	Sm	62
Europium	Eu	63
Gadolinium	Gd	64
Terbium	Tb	65
Dysprosium	Dy	66
Holmium	Ho	67
Erbium	Er	68
Thulium	Tm	69
Ytterbium	Yb	70
Lutetium	Lu	71
Hafnium	Hf	72
Tantalum	Ta	73
Tungsten	W	74
Rhenium	Re	75
Osmium	Os	76
Iridium	Ir	77
Platinum	Pt	78
Gold	Au	79
Mercury	Hg	80
Thallium	Tl	81
Lead	Pb	82
Bismuth	Bi	83
Polonium	Po	84
Astatine	At	85
Radon	Rn	86
Francium	Fr	87
Radium	Ra	88
Actinium	Ac	89
Thorium	Th	90
Protactinium	Pa	91
Uranium	U	92
Neptunium	Np	93
Plutonium	Pu	94
Americium	Am	95
Curium	Cm	96
Berkelium	Bk	97
Californium	Cf	98
Einsteinium	Es	99
Fermium	Fm	100
Mendelevium	Md	101
Nobelium	No	102
Lawrencium	Lr	103
Rutherfordium	Rf	104
Dubnium	Db	105
Seaborgium	Sg	106
Bohrium	Bh	107
Hassium	Hs	108
Meitnerium	Mt	109
Darmstadtium	Ds	110
Roentgenium	Rg	111
Copernicium	Cn	112
Nihonium	Nh	113
Flerovium	Fl	114
Moscovium	Mc	115
Livermorium	Lv	116
Tennessine	Ts	117
Oganesson	Og	118

Section 4 of 4:

Considerations for Other Rules

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Rule 3 Rule 3 requires your password to have an uppercase letter. The easiest way to get around this rule is to simply delete the previous uppercase letter you added to your password, or ensure that the uppercase letter doesn't create a one- or two-letter elemental symbol.^{[2]
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- Ideally, the uppercase letter also isn't a Roman numeral nor a vowel, to avoid messing up other rules in the game.
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Rule 7 To beat Rule 7, you must include a Roman numeral in your password. To avoid messing up this rule with Rule 18, pick XXXV for your Roman numeral (to satisfy a future rule) and avoid using any element symbols that start with I, V, X, L, C, D, or M.
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Rule 9 To satisfy Rule 9, the Roman numerals in your password must equal 35. Note that the wording of the rule says they must multiply, but the correct answer does not actually involve multiplication. This is why it's best to pick XXXV for Rule 7, and avoid using an element symbol that starts with I, V, X, L, C, D, or M.
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Rule 10 In Rule 10, you'll be required to type out a CAPTCHA to add it to your password. Oftentimes, these CAPTCHAs will have numbers in them. There are two ways to deal with this rule:
- Refresh the CAPTCHA until you get one without capital letters. There's a little arrow button next to the CAPTCHA that you can use to refresh it. This is the preferred way to deal with this rule.
  - You should also look for a CAPTCHA without any numbers to avoid messing up some of the other rules in the game.
- Type the CAPTCHA as is, then adjust the element symbols you've chosen as needed. You may not even have to adjust your element symbols if the capital letters in the CAPTCHA don't correlate to any elements on the periodic table.
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Rule 11 In Rule 11, you must type today's Wordle answer in your password. To avoid messing up Rule 18, simply type the word without a capital letter at the front.
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Rule 14 To beat Rule 14, you must type the name of the country shown in Google Maps. To avoid messing up Rule 18, type the name of the country without capitalizing the first letter.
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Rule 24 Rule 24 To satisfy Rule 24, you must include a URL to a YouTube video that matches the length of time specified by the game. There are a couple of ways to do this:
- Pick a URL that has no capital letters. This is the ideal way to go about it, since dealing with capital letters in the URL will potentially severely mess up Rule 18 (and potentially some of the other rules in the game regarding Roman numerals).
  - Ideally, the URL won't have any numbers either, to avoid messing up some of the other rules in the game.
- Adjust the elements you wrote for Rule 18 to accommodate any unintentional element symbols present in the URL. You may not even have to adjust your element symbols if the capital letters in the URL don't correlate to any elements on the periodic table.